From 9fecaf8f06a0c54ab24b0ac6903f6e15aed1428c Mon Sep 17 00:00:00 2001
From: Alexander Kiel <alexanderkiel@gmx.net>
Date: Tue, 22 Aug 2023 10:20:14 +0200
Subject: [PATCH] [WIP] CQL Cache

---
 .github/distributed-test/docker-compose.yml   |   2 +
 .../check-patient-as-of-index-missing.sh      |   9 +
 .../check-patient-as-of-index-state.sh        |   9 +
 .../scripts/test-cql-expr-cache-metrics.sh    |  19 +
 .github/scripts/test-metrics.sh               |   5 +-
 .github/workflows/build.yml                   | 194 +++++++-
 dev/blaze/dev.clj                             |   7 +-
 docs/deployment/environment-variables.md      |   1 +
 docs/implementation/cql.md                    |  40 ++
 docs/implementation/database.md               |  69 +--
 docs/monitoring/blaze.json                    | 424 +++++++++++-------
 docs/performance/cql.md                       | 144 +++++-
 docs/performance/cql/calcium-date-age.cql     |   4 +-
 docs/performance/cql/code-date-age-search.sh  |  22 -
 docs/performance/cql/code-value-search.sh     |  19 -
 docs/performance/cql/condition-all.cql        | 228 ++++++++++
 docs/performance/cql/condition-all.yml        |   5 +
 .../cql/condition-ten-frequent.cql            |  19 +
 .../cql/condition-ten-frequent.yml            |   5 +
 docs/performance/cql/condition-ten-rare.cql   |  19 +
 docs/performance/cql/condition-ten-rare.yml   |   5 +
 docs/performance/cql/condition-two.cql        |  13 +
 docs/performance/cql/condition-two.yml        |   5 +
 docs/performance/cql/hemoglobin-date-age.cql  |   4 +-
 docs/performance/cql/search.sh                |  19 +
 docs/performance/cql/simple-code-search.sh    |  19 -
 docs/performance/cql/util.sh                  |   5 +-
 docs/performance/synthea/README.md            |   4 +-
 modules/admin-api/.clj-kondo/config.edn       |   3 +-
 modules/admin-api/deps.edn                    |   5 +-
 modules/admin-api/src/blaze/admin_api.clj     |  85 +++-
 .../admin-api/test/blaze/admin_api_test.clj   |  50 ++-
 modules/byte-buffer/src/blaze/byte_buffer.clj |  13 +-
 modules/cache-collector/.clj-kondo/config.edn |  20 +
 modules/cache-collector/Makefile              |  22 +
 modules/cache-collector/deps.edn              |  45 ++
 .../src/blaze}/cache_collector.clj            |  35 +-
 .../src/blaze}/cache_collector/protocols.clj  |   2 +-
 .../src/blaze/cache_collector/spec.clj        |   8 +
 .../test/blaze}/cache_collector_test.clj      |  58 +--
 modules/cache-collector/tests.edn             |   5 +
 modules/cql/.clj-kondo/config.edn             |   5 +-
 modules/cql/src/blaze/elm/code.clj            |   2 +
 modules/cql/src/blaze/elm/compiler.clj        |   4 +
 .../elm/compiler/arithmetic_operators.clj     |  26 +-
 .../blaze/elm/compiler/clinical_operators.clj |   2 +
 .../elm/compiler/comparison_operators.clj     |   5 +
 .../elm/compiler/conditional_operators.clj    | 101 +++--
 modules/cql/src/blaze/elm/compiler/core.clj   |  24 +-
 .../elm/compiler/date_time_operators.clj      |  97 ++--
 .../cql/src/blaze/elm/compiler/expr_cache.clj |  61 +++
 .../src/blaze/elm/compiler/external_data.clj  |  44 +-
 .../cql/src/blaze/elm/compiler/function.clj   |   3 +
 .../blaze/elm/compiler/interval_operators.clj |  29 ++
 .../cql/src/blaze/elm/compiler/library.clj    |   5 +-
 .../src/blaze/elm/compiler/library_spec.clj   |   6 +-
 .../src/blaze/elm/compiler/list_operators.clj |  68 ++-
 .../blaze/elm/compiler/logical_operators.clj  |  92 ++--
 modules/cql/src/blaze/elm/compiler/macros.clj | 374 +++++++++++----
 .../cql/src/blaze/elm/compiler/queries.clj    | 131 +++---
 .../src/blaze/elm/compiler/reusing_logic.clj  |  18 +
 modules/cql/src/blaze/elm/compiler/spec.clj   |  12 +-
 .../blaze/elm/compiler/string_operators.clj   | 228 ++++++----
 .../blaze/elm/compiler/structured_values.clj  |  53 ++-
 .../src/blaze/elm/compiler/type_operators.clj |  24 +-
 modules/cql/src/blaze/elm/compiler_spec.clj   |   7 +
 modules/cql/src/blaze/elm/expression.clj      |   8 +-
 modules/cql/src/blaze/elm/expression/spec.clj |  12 +-
 modules/cql/src/blaze/elm/expression_spec.clj |   5 +
 .../compiler/conditional_operators_test.clj   |  30 +-
 .../blaze/elm/compiler/expr_cache_spec.clj    |  12 +
 .../blaze/elm/compiler/external_data_test.clj |   9 +-
 .../test/blaze/elm/compiler/library_test.clj  |  21 +-
 .../elm/compiler/list_operators_test.clj      |  91 +++-
 .../test/blaze/elm/compiler/queries_test.clj  |  66 +--
 .../cql/test/blaze/elm/compiler/test_util.clj |   3 +-
 .../src/blaze/db/impl/protocols.clj           |   4 +-
 modules/db-stub/src/blaze/db/api_stub.clj     |   6 +-
 modules/db/.clj-kondo/config.edn              |   1 +
 modules/db/deps.edn                           |   6 +
 modules/db/src/blaze/db/api.clj               |   7 +
 .../db/src/blaze/db/cache_collector/spec.clj  |   8 -
 modules/db/src/blaze/db/impl/batch_db.clj     |  18 +-
 modules/db/src/blaze/db/impl/db.clj           |  10 +
 .../src/blaze/db/impl/index/patient_as_of.clj |  87 ++++
 modules/db/src/blaze/db/node.clj              |  58 ++-
 .../src/blaze/db/node/patient_as_of_index.clj |  14 +
 modules/db/src/blaze/db/node/tx_indexer.clj   |   4 +-
 .../src/blaze/db/node/tx_indexer/verify.clj   |  59 ++-
 modules/db/src/blaze/db/node/version.clj      |   9 +-
 modules/db/src/blaze/db/resource_cache.clj    |   2 +-
 .../db/src/blaze/db/search_param_registry.clj |  41 +-
 .../blaze/db/search_param_registry_spec.clj   |   3 +-
 .../db/test-perf/blaze/db/api_test_perf.clj   |   1 +
 modules/db/test/blaze/db/api_test.clj         |  36 ++
 .../db/test/blaze/db/impl/batch_db_spec.clj   |   1 +
 modules/db/test/blaze/db/impl/db_spec.clj     |   1 +
 .../db/impl/index/patient_as_of_spec.clj      |  26 ++
 .../db/impl/index/patient_as_of_test_util.clj |  16 +
 .../db/node/patient_as_of_index_spec.clj      |  15 +
 .../db/node/patient_as_of_index_test.clj      |  49 ++
 .../blaze/db/node/tx_indexer/verify_spec.clj  |   6 +-
 .../blaze/db/node/tx_indexer/verify_test.clj  | 158 ++++++-
 .../db/test/blaze/db/node/tx_indexer_spec.clj |   5 +-
 modules/db/test/blaze/db/node_test.clj        |  12 +
 .../db/test/blaze/db/resource_cache_test.clj  |   2 +-
 .../blaze/db/search_param_registry_test.clj   |  23 +-
 modules/db/test/blaze/db/test_util.clj        |   6 +-
 modules/executor/src/blaze/executors.clj      |  23 +-
 .../.clj-kondo/config.edn                     |   1 +
 .../blaze/fhir/operation/evaluate_measure.clj |  43 ++
 .../operation/evaluate_measure/measure.clj    |  43 +-
 .../fhir/operation/evaluate_measure/spec.clj  |   4 +
 .../operation/evaluate_measure/cql/spec.clj   |  17 +-
 .../operation/evaluate_measure/cql_test.clj   |   2 +
 .../measure/stratifier_test.clj               |   1 +
 .../evaluate_measure/measure_spec.clj         |  20 +-
 .../evaluate_measure/measure_test.clj         |   8 +-
 .../fhir/operation/evaluate_measure_test.clj  |  23 +
 .../src/blaze/rest_api/middleware/metrics.clj |   6 +-
 modules/scheduler/src/blaze/scheduler.clj     |  19 +-
 .../src/blaze/scheduler/protocol.clj          |   1 +
 profiling/blaze/profiling.clj                 |  14 +-
 resources/blaze.edn                           |  40 +-
 src/blaze/system.clj                          |   2 +-
 125 files changed, 3326 insertions(+), 982 deletions(-)
 create mode 100755 .github/scripts/check-patient-as-of-index-missing.sh
 create mode 100755 .github/scripts/check-patient-as-of-index-state.sh
 create mode 100755 .github/scripts/test-cql-expr-cache-metrics.sh
 create mode 100644 docs/implementation/cql.md
 delete mode 100755 docs/performance/cql/code-date-age-search.sh
 delete mode 100755 docs/performance/cql/code-value-search.sh
 create mode 100644 docs/performance/cql/condition-all.cql
 create mode 100644 docs/performance/cql/condition-all.yml
 create mode 100644 docs/performance/cql/condition-ten-frequent.cql
 create mode 100644 docs/performance/cql/condition-ten-frequent.yml
 create mode 100644 docs/performance/cql/condition-ten-rare.cql
 create mode 100644 docs/performance/cql/condition-ten-rare.yml
 create mode 100644 docs/performance/cql/condition-two.cql
 create mode 100644 docs/performance/cql/condition-two.yml
 create mode 100755 docs/performance/cql/search.sh
 delete mode 100755 docs/performance/cql/simple-code-search.sh
 create mode 100644 modules/cache-collector/.clj-kondo/config.edn
 create mode 100644 modules/cache-collector/Makefile
 create mode 100644 modules/cache-collector/deps.edn
 rename modules/{db/src/blaze/db => cache-collector/src/blaze}/cache_collector.clj (75%)
 rename modules/{db/src/blaze/db => cache-collector/src/blaze}/cache_collector/protocols.clj (62%)
 create mode 100644 modules/cache-collector/src/blaze/cache_collector/spec.clj
 rename modules/{db/test/blaze/db => cache-collector/test/blaze}/cache_collector_test.clj (63%)
 create mode 100644 modules/cache-collector/tests.edn
 create mode 100644 modules/cql/src/blaze/elm/compiler/expr_cache.clj
 create mode 100644 modules/cql/test/blaze/elm/compiler/expr_cache_spec.clj
 delete mode 100644 modules/db/src/blaze/db/cache_collector/spec.clj
 create mode 100644 modules/db/src/blaze/db/impl/index/patient_as_of.clj
 create mode 100644 modules/db/src/blaze/db/node/patient_as_of_index.clj
 create mode 100644 modules/db/test/blaze/db/impl/index/patient_as_of_spec.clj
 create mode 100644 modules/db/test/blaze/db/impl/index/patient_as_of_test_util.clj
 create mode 100644 modules/db/test/blaze/db/node/patient_as_of_index_spec.clj
 create mode 100644 modules/db/test/blaze/db/node/patient_as_of_index_test.clj

diff --git a/.github/distributed-test/docker-compose.yml b/.github/distributed-test/docker-compose.yml
index 2791601d0..4201ceb43 100644
--- a/.github/distributed-test/docker-compose.yml
+++ b/.github/distributed-test/docker-compose.yml
@@ -81,6 +81,7 @@ services:
       DB_CASSANDRA_MAX_CONCURRENT_REQUESTS: "128"
       DB_RESOURCE_CACHE_SIZE: "100000"
       LOG_LEVEL: "debug"
+      ENABLE_FRONTEND: "true"
     ports:
     - "8081:8081"
     volumes:
@@ -111,6 +112,7 @@ services:
       DB_CASSANDRA_MAX_CONCURRENT_REQUESTS: "128"
       DB_RESOURCE_CACHE_SIZE: "100000"
       LOG_LEVEL: "debug"
+      ENABLE_FRONTEND: "true"
     ports:
     - "8082:8081"
     volumes:
diff --git a/.github/scripts/check-patient-as-of-index-missing.sh b/.github/scripts/check-patient-as-of-index-missing.sh
new file mode 100755
index 000000000..fdb175dfb
--- /dev/null
+++ b/.github/scripts/check-patient-as-of-index-missing.sh
@@ -0,0 +1,9 @@
+#!/bin/bash
+
+SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
+. "$SCRIPT_DIR/util.sh"
+
+BASE="http://localhost:8080/fhir"
+curl -s "$BASE/__admin/rocksdb/index/column-families" | jq -r '."column-families"[]' | grep -q "patient-as-of-index"
+
+test "exit code" "$?" "1"
diff --git a/.github/scripts/check-patient-as-of-index-state.sh b/.github/scripts/check-patient-as-of-index-state.sh
new file mode 100755
index 000000000..77968e9c7
--- /dev/null
+++ b/.github/scripts/check-patient-as-of-index-state.sh
@@ -0,0 +1,9 @@
+#!/bin/bash -e
+
+SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
+. "$SCRIPT_DIR/util.sh"
+
+BASE="http://localhost:8080/fhir"
+STATE="$(curl -s "$BASE/__admin/db/index/column-families/patient-as-of-index/state" | jq -r .type)"
+
+test "state" "$STATE" "$1"
diff --git a/.github/scripts/test-cql-expr-cache-metrics.sh b/.github/scripts/test-cql-expr-cache-metrics.sh
new file mode 100755
index 000000000..f3f723891
--- /dev/null
+++ b/.github/scripts/test-cql-expr-cache-metrics.sh
@@ -0,0 +1,19 @@
+#!/bin/bash -e
+
+SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
+. "$SCRIPT_DIR/util.sh"
+
+URL="http://localhost:8081/metrics"
+
+num-metrics() {
+  NAME="$1"
+  FILTER="$2"
+  curl -s "$URL" | grep "$NAME" | grep -c "$FILTER"
+}
+
+# CQL expression cache is available
+test "blaze_cache_estimated_size cql-expr-cache" "$(num-metrics "blaze_cache_estimated_size" "name=\"cql-expr-cache\"")" "1"
+
+# other caches are still available
+test "blaze_cache_estimated_size tx-cache" "$(num-metrics "blaze_cache_estimated_size" "name=\"tx-cache\"")" "1"
+test "blaze_cache_estimated_size resource-cache" "$(num-metrics "blaze_cache_estimated_size" "name=\"resource-cache\"")" "1"
diff --git a/.github/scripts/test-metrics.sh b/.github/scripts/test-metrics.sh
index a739a5c2e..b57741b8a 100755
--- a/.github/scripts/test-metrics.sh
+++ b/.github/scripts/test-metrics.sh
@@ -15,6 +15,5 @@ test "blaze_rocksdb_block_cache_data_miss index" "$(num-metrics "blaze_rocksdb_b
 test "blaze_rocksdb_block_cache_data_miss transaction" "$(num-metrics "blaze_rocksdb_block_cache_data_miss" "name=\"transaction\"")" "1"
 test "blaze_rocksdb_block_cache_data_miss resource" "$(num-metrics "blaze_rocksdb_block_cache_data_miss" "name=\"resource\"")" "1"
 
-test "blaze_rocksdb_table_reader_usage_bytes index" "$(num-metrics "blaze_rocksdb_table_reader_usage_bytes" "name=\"index\"")" "14"
-test "blaze_rocksdb_table_reader_usage_bytes transaction" "$(num-metrics "blaze_rocksdb_table_reader_usage_bytes" "name=\"transaction\"")" "1"
-test "blaze_rocksdb_table_reader_usage_bytes resource" "$(num-metrics "blaze_rocksdb_table_reader_usage_bytes" "name=\"resource\"")" "1"
+test "blaze_cache_estimated_size tx-cache" "$(num-metrics "blaze_cache_estimated_size" "name=\"tx-cache\"")" "1"
+test "blaze_cache_estimated_size resource-cache" "$(num-metrics "blaze_cache_estimated_size" "name=\"resource-cache\"")" "1"
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index ee45276d2..7daa46aad 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -39,6 +39,7 @@ jobs:
         - anomaly
         - async
         - byte-buffer
+        - cache-collector
         - cassandra
         - coll
         - cql
@@ -259,6 +260,143 @@ jobs:
       with:
         sarif_file: trivy-results.sarif
 
+  cql-expr-cache-test:
+    needs: build
+    runs-on: ubuntu-22.04
+
+    steps:
+    - name: Check out Git repository
+      uses: actions/checkout@v3
+
+    - name: Install Blazectl
+      run: .github/scripts/install-blazectl.sh
+
+    - name: Download Blaze Image
+      uses: actions/download-artifact@v3
+      with:
+        name: blaze-image
+        path: /tmp
+
+    - name: Load Blaze Image
+      run: docker load --input /tmp/blaze.tar
+
+    - name: Run Blaze
+      run: docker run --name blaze -d -e JAVA_TOOL_OPTIONS=-Xmx2g -e ENABLE_FRONTEND=true -e CQL_EXPR_CACHE_SIZE=1000 -p 8080:8080 -p 8081:8081 -v blaze-data:/app/data blaze:latest
+
+    - name: Wait for Blaze
+      run: .github/scripts/wait-for-url.sh  http://localhost:8080/health
+
+    - name: Docker Logs
+      run: docker logs blaze
+
+    - name: Check Capability Statement
+      run: .github/scripts/check-capability-statement.sh
+
+    - name: Ensure that the State of PatientAsOf Index is Current
+      run: .github/scripts/check-patient-as-of-index-state.sh current
+
+    - name: Load Data
+      run: blazectl --no-progress --server http://localhost:8080/fhir upload .github/test-data/synthea
+
+    - name: Prometheus Metrics
+      run: .github/scripts/test-cql-expr-cache-metrics.sh
+
+    - name: Check Total-Number of Resources are 92114
+      run: .github/scripts/check-total-number-of-resources.sh 92114
+
+    - name: Evaluate CQL Query 1
+      run: .github/scripts/evaluate-measure.sh q1 56
+
+    - name: Evaluate CQL Query 1 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl.sh q1 56
+
+    - name: Evaluate CQL Query 1 - Subject List
+      run: .github/scripts/evaluate-measure-subject-list.sh q1 56
+
+    - name: Evaluate CQL Query 1 on Individual Patients
+      run: .github/scripts/evaluate-patient-q1-measure.sh
+
+    - name: Evaluate CQL Query 2
+      run: .github/scripts/evaluate-measure.sh q2 42
+
+    - name: Evaluate CQL Query 2 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl.sh q2 42
+
+    - name: Evaluate CQL Query 2 - Subject List
+      run: .github/scripts/evaluate-measure-subject-list.sh q2 42
+
+    - name: Evaluate CQL Query 4
+      run: .github/scripts/evaluate-measure.sh q4 0
+
+    - name: Evaluate CQL Query 4 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl.sh q4 0
+
+    - name: Evaluate CQL Query 4 - Subject List
+      run: .github/scripts/evaluate-measure-subject-list.sh q4 0
+
+    - name: Evaluate CQL Query 7
+      run: .github/scripts/evaluate-measure.sh q7 81
+
+    - name: Evaluate CQL Query 7 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl.sh q7 81
+
+    - name: Evaluate CQL Query 7 - Subject List
+      run: .github/scripts/evaluate-measure-subject-list.sh q7 81
+
+    - name: Evaluate CQL Query 14
+      run: .github/scripts/evaluate-measure.sh q14 96
+
+    - name: Evaluate CQL Query 14 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl.sh q14 96
+
+    - name: Evaluate CQL Query 14 - Subject List
+      run: .github/scripts/evaluate-measure-subject-list.sh q14 96
+
+    - name: Evaluate CQL Query 17
+      run: .github/scripts/evaluate-measure.sh q17 120
+
+    - name: Evaluate CQL Query 17 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl.sh q17 120
+
+    - name: Evaluate CQL Query 17 - Subject List
+      run: .github/scripts/evaluate-measure-subject-list.sh q17 120
+
+    - name: Evaluate CQL Query 20 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl-stratifier.sh q20-stratifier-city 120
+
+    - name: Evaluate CQL Query 21 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl-stratifier.sh q21-stratifier-city-of-only-women 64
+
+    - name: Evaluate CQL Query 26 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl-stratifier.sh q26-stratifier-bmi 120
+
+    - name: Evaluate CQL Query 27 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl-stratifier.sh q27-stratifier-calculated-bmi 120
+
+    - name: Evaluate CQL Query 32 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl-stratifier.sh q32-stratifier-underweight 120
+
+    - name: Evaluate CQL Query 36
+      run: .github/scripts/evaluate-measure.sh q36-parameter 86
+
+    - name: Evaluate CQL Query 36 - Subject List
+      run: .github/scripts/evaluate-measure-subject-list.sh q36-parameter 86
+
+    - name: Evaluate CQL Query 34
+      run: .github/scripts/evaluate-measure.sh q37-overlaps 24
+
+    - name: Evaluate CQL Query 34 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl.sh q37-overlaps 24
+
+    - name: Evaluate CQL Query 34 - Subject List
+      run: .github/scripts/evaluate-measure-subject-list.sh q37-overlaps 24
+
+    - name: Evaluate CQL Query 46
+      run: .github/scripts/evaluate-measure.sh q46-between-date 19
+
+    - name: Evaluate CQL Query 46 using Blazectl
+      run: .github/scripts/evaluate-measure-blazectl.sh q46-between-date 19
+
   integration-test:
     needs: build
     runs-on: ubuntu-22.04
@@ -280,7 +418,7 @@ jobs:
       run: docker load --input /tmp/blaze.tar
 
     - name: Run Blaze
-      run: docker run --name blaze -d -e JAVA_TOOL_OPTIONS=-Xmx2g -p 8080:8080 -p 8081:8081 -v blaze-data:/app/data blaze:latest
+      run: docker run --name blaze -d -e JAVA_TOOL_OPTIONS=-Xmx2g -e ENABLE_FRONTEND=true -p 8080:8080 -p 8081:8081 -v blaze-data:/app/data blaze:latest
 
     - name: Wait for Blaze
       run: .github/scripts/wait-for-url.sh  http://localhost:8080/health
@@ -294,6 +432,9 @@ jobs:
     - name: Check Referential Integrity Enforced
       run: .github/scripts/check-referential-integrity-enforced.sh
 
+    - name: Ensure that the State of PatientAsOf Index is Current
+      run: .github/scripts/check-patient-as-of-index-state.sh current
+
     - name: Load Data
       run: blazectl --no-progress --server http://localhost:8080/fhir upload .github/test-data/synthea
 
@@ -1137,6 +1278,50 @@ jobs:
     - name: Fetch Patient Expecting an Error
       run: .github/scripts/fetch-resource-0-with-missing-resource-content.sh
 
+  build-patient-as-of-index-test:
+    needs: build
+    runs-on: ubuntu-22.04
+
+    steps:
+    - name: Check out Git repository
+      uses: actions/checkout@v3
+
+    - name: Install Blazectl
+      run: .github/scripts/install-blazectl.sh
+
+    - name: Download Blaze Image
+      uses: actions/download-artifact@v3
+      with:
+        name: blaze-image
+        path: /tmp
+
+    - name: Load Blaze Image
+      run: docker load --input /tmp/blaze.tar
+
+    - name: Run Blaze v0.22
+      run: docker run --name blaze -d -e JAVA_TOOL_OPTIONS=-Xmx2g -e ENABLE_FRONTEND=true -p 8080:8080 -v blaze-data:/app/data samply/blaze:0.22
+
+    - name: Wait for Blaze
+      run: .github/scripts/wait-for-url.sh  http://localhost:8080/health
+
+    - name: Load Data
+      run: blazectl --no-progress --server http://localhost:8080/fhir upload .github/test-data/synthea
+
+    - name: Ensure that the PatientAsOf Index does not exist
+      run: .github/scripts/check-patient-as-of-index-missing.sh
+
+    - name: Shut down Blaze
+      run: docker stop blaze && docker rm blaze
+
+    - name: Run Latest Blaze
+      run: docker run --name blaze -d -e JAVA_TOOL_OPTIONS=-Xmx2g -e ENABLE_FRONTEND=true -e LOG_LEVEL=debug -p 8080:8080 -v blaze-data:/app/data blaze:latest
+
+    - name: Wait for Blaze
+      run: .github/scripts/wait-for-url.sh  http://localhost:8080/health
+
+    - name: Ensure that the State of PatientAsOf Index is Current
+      run: .github/scripts/check-patient-as-of-index-state.sh current
+
   distributed-test:
     needs: build
     runs-on: ubuntu-22.04
@@ -1193,6 +1378,9 @@ jobs:
     - name: Check Referential Integrity Enforced
       run: .github/scripts/check-referential-integrity-enforced.sh
 
+    - name: Ensure that the State of PatientAsOf Index is Current
+      run: .github/scripts/check-patient-as-of-index-state.sh current
+
     - name: Load Data
       run: blazectl --no-progress --server http://localhost:8080/fhir upload .github/test-data/synthea
 
@@ -1613,6 +1801,7 @@ jobs:
     needs:
     - build
     - image-scan
+    - cql-expr-cache-test
     - integration-test
     - not-enforcing-referential-integrity-test
     - small-transactions-test
@@ -1623,13 +1812,14 @@ jobs:
     - bundle-with-references-test
     - jepsen-test
     - openid-auth-test
+    - custom-search-parameters-test
     - doc-copy-data-test
     - big-binary-test
     - frontend-test
     - missing-resource-content-test
+    - build-patient-as-of-index-test
     - distributed-test
     - jepsen-distributed-test
-    - custom-search-parameters-test
     runs-on: ubuntu-22.04
     permissions:
       packages: write
diff --git a/dev/blaze/dev.clj b/dev/blaze/dev.clj
index 98f3aa7e6..3e1e2b96a 100644
--- a/dev/blaze/dev.clj
+++ b/dev/blaze/dev.clj
@@ -1,9 +1,9 @@
 (ns blaze.dev
   (:require
     [blaze.byte-string :as bs]
+    [blaze.cache-collector.protocols :as ccp]
     [blaze.db.api :as d]
     [blaze.db.api-spec]
-    [blaze.db.cache-collector.protocols :as ccp]
     [blaze.db.resource-cache :as resource-cache]
     [blaze.db.resource-store :as rs]
     [blaze.db.tx-log :as tx-log]
@@ -66,6 +66,11 @@
   (resource-cache/invalidate-all! (:blaze.db/resource-cache system))
   )
 
+;; CQL Expression Cache
+(comment
+  (str (ccp/-stats (:blaze.fhir.operation.evaluate-measure/expr-cache system)))
+  )
+
 ;; RocksDB Stats
 (comment
   (.reset (system [:blaze.db.kv.rocksdb/stats :blaze.db.index-kv-store/stats]))
diff --git a/docs/deployment/environment-variables.md b/docs/deployment/environment-variables.md
index bd00448e7..fe309e27e 100644
--- a/docs/deployment/environment-variables.md
+++ b/docs/deployment/environment-variables.md
@@ -91,6 +91,7 @@ More information about distributed deployment are available [here](distributed.m
 | ENFORCE_REFERENTIAL_INTEGRITY           | true                       | v0.14  | —      | Enforce referential integrity on resource create, update and delete.                           |
 | DB_SYNC_TIMEOUT                         | 10000                      | v0.15  | —      | Timeout in milliseconds for all reading FHIR interactions acquiring the newest database state. |
 | DB_SEARCH_PARAM_BUNDLE                  | —                          | v0.21  | —      | Name of a custom search parameter bundle file.                                                 |
+| CQL_EXPR_CACHE_SIZE                     | —                          | v0.23  | —      | Size of the CQL expression cache. Will be disabled if not given.                               |
 
 ¹ Deprecated
 
diff --git a/docs/implementation/cql.md b/docs/implementation/cql.md
new file mode 100644
index 000000000..ef0370d74
--- /dev/null
+++ b/docs/implementation/cql.md
@@ -0,0 +1,40 @@
+# CQL
+
+## Expression Cache
+
+* bloom filter
+  * the set we like to build is the set of expressions returning true
+  * if the bloom filter returns false, we can be sure that the expression is not in the set of expressions returning true, so it will certainly return false
+  * the number of expressions returning true is far less then the number of expressions returning false
+  * we'll fill the Bloom filter with the expressions that returned true
+  * the problem is the following
+    * if we don't have filled the filter with all expression, the answer we get has no value
+      * we don't know whether the expression isn't in the set because we didn't put it there or because if returned false
+  * but we could use two filters
+    * one for all expressions returning true and one for all returning false
+    * if the expression isn't in both filters, it is new and so we have the evaluate it
+  * we could use a bloom filter for each expression
+    * then we would see whether we have a bloom filter or not
+    * we would insert Patients for which the expression returns true
+    * the first query evaluation is only used for insertion
+    * after that we mark the filter as ready for query
+    * now we can determine whether a expression is not true for a certain Patient
+    * 
+
+* we'll use one Bloom filter per expression
+* that Bloom filters will be stored in a Caffeine cache by expression hash
+* each Bloom filter will be assigned the t of its creation
+* the Bloom filters of all expressions of a query will be collected at the start of the query evaluation
+* if a Bloom filter isn't found, its calculation will be queued and carried out asynchronously
+* existing Bloom filters are immutable and will be used in query evaluation
+  * the Patient ID will be used to test whether this Patient isn't in the Bloom filter
+  * if the Patient ID wasn't found, the expression will return false
+  * if the Patient ID is found, the expression will be evaluated normally
+
+### Bloom Filter Calculation
+
+* the Bloom filter will be calculated for a particular exists expression
+* it will be calculated based on a database with a particular t
+* that t will be assigned to the Bloom filter
+* the calculation will evaluate the expression for each patent of the database
+* the ID's of Patients for which the expression returns true will be put into the Bloom filter
diff --git a/docs/implementation/database.md b/docs/implementation/database.md
index 6da5c8b8d..966bc65ca 100644
--- a/docs/implementation/database.md
+++ b/docs/implementation/database.md
@@ -38,16 +38,17 @@ There are two different sets of indices, ones which depend on the database value
 
 ### Indices depending on t
 
-| Name         | Key Parts | Value                         |
-|--------------|-----------|-------------------------------|
-| ResourceAsOf | type id t | content-hash, num-changes, op |
-| TypeAsOf     | type t id | content-hash, num-changes, op |
-| SystemAsOf   | t type id | content-hash, num-changes, op |
-| TxSuccess    | t         | instant                       |
-| TxError      | t         | anomaly                       |
-| TByInstant   | instant   | t                             |
-| TypeStats    | type t    | total, num-changes            |
-| SystemStats  | t         | total, num-changes            |
+| Name         | Key Parts        | Value                         |
+|--------------|------------------|-------------------------------|
+| ResourceAsOf | type id t        | content-hash, num-changes, op |
+| TypeAsOf     | type t id        | content-hash, num-changes, op |
+| SystemAsOf   | t type id        | content-hash, num-changes, op |
+| PatientAsOf  | pat-id t type id | content-hash, num-changes, op |
+| TxSuccess    | t                | instant                       |
+| TxError      | t                | anomaly                       |
+| TByInstant   | instant          | t                             |
+| TypeStats    | type t           | total, num-changes            |
+| SystemStats  | t                | total, num-changes            |
 
 #### ResourceAsOf
 
@@ -83,12 +84,16 @@ In addition to direct resource lookup, the `ResourceAsOf` index is used for list
 
 #### TypeAsOf
 
-The `TypeAsOf` index contains the same information as the `ResourceAsOf` index with the difference that the components of the key are ordered `type`,  `t` and  `id` instead of `type`, `id` and `t`. The index is used for listing all versions of all resources of a particular type. Such history listings start with the `t` of the database value going into the past. This is done by not only choosing the resource version with the latest `t` less or equal the database values `t` but instead using all older versions. Such versions even include deleted versions because in FHIR it is allowed to bring back a resource to a new life after it was already deleted. The listing is done by simply scanning through the index in reverse. Because the key is ordered by `type`,  `t` and  `id`, the entries will be first ordered by time, newest first, and second by resource identifier.
+The `TypeAsOf` index contains the same information as the `ResourceAsOf` index with the difference that the components of the key are ordered `type`,  `t` and `id` instead of `type`, `id` and `t`. The index is used for listing all versions of all resources of a particular type. Such history listings start with the `t` of the database value going into the past. This is done by not only choosing the resource version with the latest `t` less or equal the database values `t` but instead using all older versions. Such versions even include deleted versions because in FHIR it is allowed to bring back a resource to a new life after it was already deleted. The listing is done by simply scanning through the index in reverse. Because the key is ordered by `type`,  `t` and  `id`, the entries will be first ordered by time, newest first, and second by resource identifier.
 
 #### SystemAsOf
 
 In the same way the `TypeAsOf` index uses a different key ordering in comparison to the `ResourceAsOf` index, the `SystemAsOf` index will use the key order `t`, `type` and `id` in order to provide a global time axis order by resource type and by identifier secondarily.
 
+#### PatientAsOf
+
+The `PatientAsOf` index works like the `SystemAsOf` index but for each Patient individually. It contains all changes to resources in the compartment of a particular Patient on reverse chronological order. Using the `PatientAsOf` index it's possible to create a history of all changes in the Patient compartment or detect the `t` of the last change. The CQL cache uses this index to invalidate cached results of expressions in the Patient context. 
+
 #### TxSuccess
 
 The `TxSuccess` index contains the real point in time, as `java.time.Instant`, successful transactions happened. In other words, this index maps each `t` which is just a monotonically increasing number to a real point in time. 
@@ -115,23 +120,24 @@ The `SystemStats` index keeps track of the total number of resources, and the nu
 
 The indices not depending on `t` directly point to the resource versions by their content hash. 
 
-| Name                                | Key Parts                                                        | Value |
-|-------------------------------------|------------------------------------------------------------------|-------|
-| SearchParamValueResource            | search-param, type, value, id, content-hash                      | -     |
-| ResourceSearchParamValue            | type, id, content-hash, search-param, value                      | -     |
-| CompartmentSearchParamValueResource | co-c-hash, co-res-id, search-param, type, value, id, hash-prefix | -     |
-| CompartmentResource                 | co-c-hash, co-res-id, tid, id                                    | -     |
-| SearchParam                         | code, tid                                                        | id    |
-| ActiveSearchParams                  | id                                                               | -     |
+| Name                                | Key Parts                                                      | Value |
+|-------------------------------------|----------------------------------------------------------------|-------|
+| SearchParamValueResource            | search-param, type, value, id, hash-prefix                     | -     |
+| ResourceSearchParamValue            | type, id, content-hash, search-param, value                    | -     |
+| CompartmentSearchParamValueResource | comp-code, comp-id, search-param, type, value, id, hash-prefix | -     |
+| CompartmentResource                 | comp-code, comp-id, type, id                                   | -     |
+| SearchParam                         | code, type                                                     | id    |
+| ActiveSearchParams                  | id                                                             | -     |
 
 #### SearchParamValueResource
 
 The `SearchParamValueResource` index contains all values from resources that are reachable from search parameters. The components of its key are:
-* `search-param` - a 4-byte hash of the search parameters code used to identify the search parameter
-* `type` - a 4-byte hash of the resource type
-* `value` - the encoded value of the resource reachable by the search parameters FHIRPath expression. The encoding depends on the search parameters type.
-* `id` - the logical id of the resource
-* `content-hash` - a 4-byte prefix of the content-hash of the resource version
+
+ * `search-param` - a 4-byte hash of the search parameters code used to identify the search parameter
+ * `type` - a 4-byte hash of the resource type
+ * `value` - the encoded value of the resource reachable by the search parameters FHIRPath expression. The encoding depends on the search parameters type.
+ * `id` - the logical id of the resource
+ * `content-hash` - a 4-byte prefix of the content-hash of the resource version
 
 The way the `SearchParamValueResource` index is used, depends on the type of the search parameter. The following sections will explain this in detail for each type:
 
@@ -207,11 +213,20 @@ That tuples are further processed against the `ResourceAsOf` index in order to c
 
 **TODO: continue...**
 
+#### CompartmentResource
+
+The `CompartmentResource` index contains all resources that belong to a certain compartment. The components of its key are:
+
+ * `comp-code` - a 4-byte hash of the compartment code, ex. `Patient`
+ * `comp-id` - the logical id of the compartment, ex. the logical id of the Patient
+ * `type` - a 4-byte hash of the resource type of the resource that belongs to the compartment, ex. `Observation`
+ * `id` - the logical id of the resource that belongs to the compartment, ex. the logical id of the Observation
+
 ## Transaction Handling
 
-* a transaction bundle is POST'ed to one arbitrary node
-* this node submits the transaction commands to the central transaction log
-* all nodes (inkl. the transaction submitter) receive the transaction commands from the central transaction log
+ * a transaction bundle is POST'ed to one arbitrary node
+ * this node submits the transaction commands to the central transaction log
+ * all nodes (inkl. the transaction submitter) receive the transaction commands from the central transaction log
 
 ### Transaction Commands
 
diff --git a/docs/monitoring/blaze.json b/docs/monitoring/blaze.json
index 33d5b5886..0cd8aaac3 100644
--- a/docs/monitoring/blaze.json
+++ b/docs/monitoring/blaze.json
@@ -24,7 +24,7 @@
   "editable": true,
   "fiscalYearStartMonth": 0,
   "graphTooltip": 1,
-  "id": 74,
+  "id": 79,
   "links": [
     {
       "asDropdown": false,
@@ -447,7 +447,7 @@
             "uid": "${DS_PROMETHEUS}"
           },
           "editorMode": "code",
-          "expr": "blaze_db_cache_estimated_size{job=\"$job\",instance=\"$instance\",name=\"resource-cache\"}",
+          "expr": "blaze_cache_estimated_size{job=\"$job\",instance=\"$instance\",name=\"resource-cache\"}",
           "hide": false,
           "interval": "",
           "legendFormat": "",
@@ -546,7 +546,7 @@
             "uid": "${DS_PROMETHEUS}"
           },
           "editorMode": "code",
-          "expr": "rate(blaze_db_cache_hits_total{job=\"$job\",instance=\"$instance\", name=\"resource-cache\"}[1m]) / (rate(blaze_db_cache_hits_total[1m]) + rate(blaze_db_cache_misses_total[1m]))",
+          "expr": "rate(blaze_cache_hits_total{job=\"$job\",instance=\"$instance\", name=\"resource-cache\"}[1m]) / (rate(blaze_cache_hits_total[1m]) + rate(blaze_cache_misses_total[1m]))",
           "hide": false,
           "interval": "",
           "legendFormat": "",
@@ -644,7 +644,7 @@
             "uid": "${DS_PROMETHEUS}"
           },
           "editorMode": "code",
-          "expr": "rate(blaze_db_cache_load_successes_total{job=\"$job\",instance=\"$instance\",name=\"resource-cache\"}[1m])",
+          "expr": "rate(blaze_cache_load_successes_total{job=\"$job\",instance=\"$instance\",name=\"resource-cache\"}[1m])",
           "hide": false,
           "interval": "",
           "legendFormat": "",
@@ -742,7 +742,7 @@
             "uid": "${DS_PROMETHEUS}"
           },
           "editorMode": "code",
-          "expr": "rate(blaze_db_cache_evictions_total{job=\"$job\",instance=\"$instance\",name=\"resource-cache\"}[1m])",
+          "expr": "rate(blaze_cache_evictions_total{job=\"$job\",instance=\"$instance\",name=\"resource-cache\"}[1m])",
           "hide": false,
           "interval": "",
           "legendFormat": "",
@@ -759,7 +759,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 15
+        "y": 14
       },
       "id": 160,
       "panels": [],
@@ -831,7 +831,7 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 16
+        "y": 15
       },
       "id": 162,
       "links": [],
@@ -898,7 +898,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 22
+        "y": 21
       },
       "id": 68,
       "panels": [],
@@ -981,7 +981,7 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 23
+        "y": 22
       },
       "id": 63,
       "options": {
@@ -1105,7 +1105,7 @@
         "h": 6,
         "w": 8,
         "x": 8,
-        "y": 23
+        "y": 22
       },
       "id": 119,
       "options": {
@@ -1205,7 +1205,7 @@
         "h": 6,
         "w": 8,
         "x": 16,
-        "y": 23
+        "y": 22
       },
       "id": 121,
       "options": {
@@ -1305,7 +1305,7 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 29
+        "y": 28
       },
       "id": 69,
       "options": {
@@ -1429,7 +1429,7 @@
         "h": 6,
         "w": 8,
         "x": 8,
-        "y": 29
+        "y": 28
       },
       "id": 79,
       "options": {
@@ -1529,7 +1529,7 @@
         "h": 6,
         "w": 8,
         "x": 16,
-        "y": 29
+        "y": 28
       },
       "id": 80,
       "options": {
@@ -1628,7 +1628,7 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 35
+        "y": 34
       },
       "id": 64,
       "options": {
@@ -1752,7 +1752,7 @@
         "h": 6,
         "w": 8,
         "x": 8,
-        "y": 35
+        "y": 34
       },
       "id": 65,
       "options": {
@@ -1876,7 +1876,7 @@
         "h": 6,
         "w": 8,
         "x": 16,
-        "y": 35
+        "y": 34
       },
       "id": 95,
       "options": {
@@ -1930,6 +1930,7 @@
         "type": "prometheus",
         "uid": "${DS_PROMETHEUS}"
       },
+      "description": "Open Iterators. Should be not growing unbounded. If not please file an issue.",
       "fieldConfig": {
         "defaults": {
           "color": {
@@ -1989,15 +1990,12 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 41
+        "y": 40
       },
-      "id": 113,
-      "links": [],
+      "id": 266,
       "options": {
         "legend": {
-          "calcs": [
-            "mean"
-          ],
+          "calcs": [],
           "displayMode": "list",
           "placement": "bottom",
           "showLegend": false
@@ -2016,18 +2014,15 @@
           },
           "editorMode": "code",
           "exemplar": true,
-          "expr": "rate(blaze_rocksdb_compaction_seconds_total{job=\"$job\",instance=\"$instance\", name=\"$database\"}[1m])",
-          "format": "time_series",
+          "expr": "blaze_rocksdb_iterators_created_total{job=\"$job\",instance=\"$instance\", name=\"$database\"} - blaze_rocksdb_iterators_deleted_total",
+          "hide": false,
           "interval": "",
-          "intervalFactor": 2,
-          "legendFormat": " {{name}}",
-          "metric": "process_cpu_seconds_total",
+          "legendFormat": "created",
           "range": true,
-          "refId": "A",
-          "step": 10
+          "refId": "A"
         }
       ],
-      "title": "Compaction Seconds",
+      "title": "Iterators Open",
       "type": "timeseries"
     },
     {
@@ -2094,7 +2089,7 @@
         "h": 6,
         "w": 8,
         "x": 8,
-        "y": 41
+        "y": 40
       },
       "id": 114,
       "links": [],
@@ -2199,7 +2194,7 @@
         "h": 6,
         "w": 8,
         "x": 16,
-        "y": 41
+        "y": 40
       },
       "id": 115,
       "links": [],
@@ -2296,7 +2291,7 @@
               }
             ]
           },
-          "unit": "ops"
+          "unit": "short"
         },
         "overrides": []
       },
@@ -2304,12 +2299,15 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 47
+        "y": 46
       },
-      "id": 155,
+      "id": 113,
+      "links": [],
       "options": {
         "legend": {
-          "calcs": [],
+          "calcs": [
+            "mean"
+          ],
           "displayMode": "list",
           "placement": "bottom",
           "showLegend": false
@@ -2328,15 +2326,18 @@
           },
           "editorMode": "code",
           "exemplar": true,
-          "expr": "rate(blaze_rocksdb_wal_syncs_total{job=\"$job\",instance=\"$instance\", name=\"$database\"}[1m])",
-          "hide": false,
+          "expr": "rate(blaze_rocksdb_compaction_seconds_total{job=\"$job\",instance=\"$instance\", name=\"$database\"}[1m])",
+          "format": "time_series",
           "interval": "",
-          "legendFormat": "{{name}}",
+          "intervalFactor": 2,
+          "legendFormat": " {{name}}",
+          "metric": "process_cpu_seconds_total",
           "range": true,
-          "refId": "A"
+          "refId": "A",
+          "step": 10
         }
       ],
-      "title": "WAL Sync",
+      "title": "Compaction Seconds",
       "type": "timeseries"
     },
     {
@@ -2404,7 +2405,7 @@
         "h": 6,
         "w": 8,
         "x": 8,
-        "y": 47
+        "y": 46
       },
       "id": 94,
       "options": {
@@ -2504,7 +2505,7 @@
         "h": 6,
         "w": 8,
         "x": 16,
-        "y": 47
+        "y": 46
       },
       "id": 97,
       "options": {
@@ -2544,7 +2545,6 @@
         "type": "prometheus",
         "uid": "${DS_PROMETHEUS}"
       },
-      "description": "The total number of writes ending up with a timeout.",
       "fieldConfig": {
         "defaults": {
           "color": {
@@ -2574,7 +2574,7 @@
             "spanNulls": false,
             "stacking": {
               "group": "A",
-              "mode": "normal"
+              "mode": "none"
             },
             "thresholdsStyle": {
               "mode": "off"
@@ -2604,9 +2604,9 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 53
+        "y": 52
       },
-      "id": 98,
+      "id": 155,
       "options": {
         "legend": {
           "calcs": [],
@@ -2628,7 +2628,7 @@
           },
           "editorMode": "code",
           "exemplar": true,
-          "expr": "rate(blaze_rocksdb_write_timeout_total{job=\"$job\",instance=\"$instance\", name=\"$database\"}[1m])",
+          "expr": "rate(blaze_rocksdb_wal_syncs_total{job=\"$job\",instance=\"$instance\", name=\"$database\"}[1m])",
           "hide": false,
           "interval": "",
           "legendFormat": "{{name}}",
@@ -2636,7 +2636,7 @@
           "refId": "A"
         }
       ],
-      "title": "Write Timeouts",
+      "title": "WAL Sync",
       "type": "timeseries"
     },
     {
@@ -2703,7 +2703,7 @@
         "h": 6,
         "w": 8,
         "x": 8,
-        "y": 53
+        "y": 52
       },
       "id": 112,
       "links": [],
@@ -2808,7 +2808,7 @@
         "h": 6,
         "w": 8,
         "x": 16,
-        "y": 53
+        "y": 52
       },
       "id": 154,
       "options": {
@@ -2847,7 +2847,7 @@
         "type": "prometheus",
         "uid": "${DS_PROMETHEUS}"
       },
-      "description": "",
+      "description": "The total number of writes ending up with a timeout.",
       "fieldConfig": {
         "defaults": {
           "color": {
@@ -2901,40 +2901,15 @@
           },
           "unit": "ops"
         },
-        "overrides": [
-          {
-            "__systemRef": "hideSeriesFrom",
-            "matcher": {
-              "id": "byNames",
-              "options": {
-                "mode": "exclude",
-                "names": [
-                  "index"
-                ],
-                "prefix": "All except:",
-                "readOnly": true
-              }
-            },
-            "properties": [
-              {
-                "id": "custom.hideFrom",
-                "value": {
-                  "legend": false,
-                  "tooltip": false,
-                  "viz": true
-                }
-              }
-            ]
-          }
-        ]
+        "overrides": []
       },
       "gridPos": {
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 59
+        "y": 58
       },
-      "id": 156,
+      "id": 98,
       "options": {
         "legend": {
           "calcs": [],
@@ -2956,7 +2931,7 @@
           },
           "editorMode": "code",
           "exemplar": true,
-          "expr": "rate(blaze_rocksdb_blocks_compressed_total{job=\"$job\",instance=\"$instance\", name=\"$database\"}[1m])",
+          "expr": "rate(blaze_rocksdb_write_timeout_total{job=\"$job\",instance=\"$instance\", name=\"$database\"}[1m])",
           "hide": false,
           "interval": "",
           "legendFormat": "{{name}}",
@@ -2964,7 +2939,7 @@
           "refId": "A"
         }
       ],
-      "title": "Blocks Compressed",
+      "title": "Write Timeouts",
       "type": "timeseries"
     },
     {
@@ -3057,7 +3032,7 @@
         "h": 6,
         "w": 8,
         "x": 8,
-        "y": 59
+        "y": 58
       },
       "id": 157,
       "options": {
@@ -3156,7 +3131,7 @@
         "h": 6,
         "w": 8,
         "x": 16,
-        "y": 59
+        "y": 58
       },
       "id": 234,
       "options": {
@@ -3221,7 +3196,7 @@
         "type": "prometheus",
         "uid": "${DS_PROMETHEUS}"
       },
-      "description": "Values are per Column Family and stacked.",
+      "description": "",
       "fieldConfig": {
         "defaults": {
           "color": {
@@ -3248,7 +3223,7 @@
               "type": "linear"
             },
             "showPoints": "never",
-            "spanNulls": true,
+            "spanNulls": false,
             "stacking": {
               "group": "A",
               "mode": "normal"
@@ -3273,24 +3248,48 @@
               }
             ]
           },
-          "unit": "bytes"
+          "unit": "ops"
         },
-        "overrides": []
+        "overrides": [
+          {
+            "__systemRef": "hideSeriesFrom",
+            "matcher": {
+              "id": "byNames",
+              "options": {
+                "mode": "exclude",
+                "names": [
+                  "index"
+                ],
+                "prefix": "All except:",
+                "readOnly": true
+              }
+            },
+            "properties": [
+              {
+                "id": "custom.hideFrom",
+                "value": {
+                  "legend": false,
+                  "tooltip": false,
+                  "viz": true
+                }
+              }
+            ]
+          }
+        ]
       },
       "gridPos": {
         "h": 6,
-        "w": 16,
+        "w": 8,
         "x": 0,
-        "y": 65
+        "y": 64
       },
-      "id": 186,
-      "links": [],
+      "id": 156,
       "options": {
         "legend": {
           "calcs": [],
           "displayMode": "list",
-          "placement": "right",
-          "showLegend": true
+          "placement": "bottom",
+          "showLegend": false
         },
         "tooltip": {
           "mode": "multi",
@@ -3305,19 +3304,16 @@
             "uid": "${DS_PROMETHEUS}"
           },
           "editorMode": "code",
-          "exemplar": false,
-          "expr": "blaze_rocksdb_table_reader_usage_bytes{job=\"$job\",instance=\"$instance\", name=\"$database\"}",
-          "format": "time_series",
+          "exemplar": true,
+          "expr": "rate(blaze_rocksdb_blocks_compressed_total{job=\"$job\",instance=\"$instance\", name=\"$database\"}[1m])",
+          "hide": false,
           "interval": "",
-          "intervalFactor": 1,
-          "legendFormat": "{{column_family}}",
-          "metric": "process_cpu_seconds_total",
+          "legendFormat": "{{name}}",
           "range": true,
-          "refId": "A",
-          "step": 10
+          "refId": "A"
         }
       ],
-      "title": "Table Reader Memory Usage",
+      "title": "Blocks Compressed",
       "type": "timeseries"
     },
     {
@@ -3409,8 +3405,8 @@
       "gridPos": {
         "h": 6,
         "w": 8,
-        "x": 16,
-        "y": 65
+        "x": 8,
+        "y": 64
       },
       "id": 158,
       "options": {
@@ -3445,6 +3441,110 @@
       "title": "Blocks Not Compressed",
       "type": "timeseries"
     },
+    {
+      "datasource": {
+        "type": "prometheus",
+        "uid": "${DS_PROMETHEUS}"
+      },
+      "description": "Values are per Column Family and stacked.",
+      "fieldConfig": {
+        "defaults": {
+          "color": {
+            "mode": "palette-classic"
+          },
+          "custom": {
+            "axisCenteredZero": false,
+            "axisColorMode": "text",
+            "axisLabel": "",
+            "axisPlacement": "auto",
+            "barAlignment": 0,
+            "drawStyle": "line",
+            "fillOpacity": 10,
+            "gradientMode": "none",
+            "hideFrom": {
+              "legend": false,
+              "tooltip": false,
+              "viz": false
+            },
+            "lineInterpolation": "linear",
+            "lineWidth": 1,
+            "pointSize": 5,
+            "scaleDistribution": {
+              "type": "linear"
+            },
+            "showPoints": "never",
+            "spanNulls": true,
+            "stacking": {
+              "group": "A",
+              "mode": "normal"
+            },
+            "thresholdsStyle": {
+              "mode": "off"
+            }
+          },
+          "links": [],
+          "mappings": [],
+          "min": 0,
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              {
+                "color": "green",
+                "value": null
+              },
+              {
+                "color": "red",
+                "value": 80
+              }
+            ]
+          },
+          "unit": "bytes"
+        },
+        "overrides": []
+      },
+      "gridPos": {
+        "h": 6,
+        "w": 8,
+        "x": 16,
+        "y": 64
+      },
+      "id": 186,
+      "links": [],
+      "options": {
+        "legend": {
+          "calcs": [],
+          "displayMode": "list",
+          "placement": "right",
+          "showLegend": true
+        },
+        "tooltip": {
+          "mode": "multi",
+          "sort": "none"
+        }
+      },
+      "pluginVersion": "8.4.4",
+      "targets": [
+        {
+          "datasource": {
+            "type": "prometheus",
+            "uid": "${DS_PROMETHEUS}"
+          },
+          "editorMode": "code",
+          "exemplar": false,
+          "expr": "blaze_rocksdb_table_reader_usage_bytes{job=\"$job\",instance=\"$instance\", name=\"$database\"}",
+          "format": "time_series",
+          "interval": "",
+          "intervalFactor": 1,
+          "legendFormat": "{{column_family}}",
+          "metric": "process_cpu_seconds_total",
+          "range": true,
+          "refId": "A",
+          "step": 10
+        }
+      ],
+      "title": "Table Reader Memory Usage",
+      "type": "timeseries"
+    },
     {
       "collapsed": false,
       "datasource": {
@@ -3455,7 +3555,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 71
+        "y": 70
       },
       "id": 59,
       "panels": [],
@@ -3535,7 +3635,7 @@
         "h": 6,
         "w": 24,
         "x": 0,
-        "y": 72
+        "y": 71
       },
       "id": 61,
       "links": [],
@@ -3635,7 +3735,7 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 78
+        "y": 77
       },
       "id": 62,
       "options": {
@@ -3677,7 +3777,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 84
+        "y": 83
       },
       "id": 261,
       "panels": [],
@@ -3732,8 +3832,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -3749,7 +3848,7 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 85
+        "y": 84
       },
       "id": 259,
       "options": {
@@ -3795,7 +3894,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 91
+        "y": 90
       },
       "id": 46,
       "panels": [
@@ -4098,7 +4197,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 92
+        "y": 91
       },
       "id": 86,
       "panels": [],
@@ -4163,8 +4262,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -4180,7 +4278,7 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 93
+        "y": 92
       },
       "id": 22,
       "options": {
@@ -4259,8 +4357,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -4301,7 +4398,7 @@
         "h": 6,
         "w": 8,
         "x": 8,
-        "y": 93
+        "y": 92
       },
       "id": 87,
       "options": {
@@ -4380,8 +4477,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -4397,7 +4493,7 @@
         "h": 6,
         "w": 8,
         "x": 16,
-        "y": 93
+        "y": 92
       },
       "id": 88,
       "options": {
@@ -4477,8 +4573,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -4494,7 +4589,7 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 99
+        "y": 98
       },
       "id": 90,
       "options": {
@@ -4576,8 +4671,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -4593,7 +4687,7 @@
         "h": 6,
         "w": 8,
         "x": 8,
-        "y": 99
+        "y": 98
       },
       "id": 91,
       "options": {
@@ -4675,8 +4769,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -4692,7 +4785,7 @@
         "h": 6,
         "w": 8,
         "x": 16,
-        "y": 99
+        "y": 98
       },
       "id": 92,
       "options": {
@@ -4774,8 +4867,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -4791,7 +4883,7 @@
         "h": 6,
         "w": 8,
         "x": 0,
-        "y": 105
+        "y": 104
       },
       "id": 93,
       "options": {
@@ -4835,7 +4927,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 111
+        "y": 110
       },
       "id": 103,
       "panels": [
@@ -5438,7 +5530,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 112
+        "y": 111
       },
       "id": 31,
       "panels": [
@@ -6271,7 +6363,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 113
+        "y": 112
       },
       "id": 24,
       "panels": [
@@ -6670,7 +6762,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 114
+        "y": 113
       },
       "id": 37,
       "panels": [
@@ -7175,7 +7267,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 115
+        "y": 114
       },
       "id": 34,
       "panels": [],
@@ -7238,8 +7330,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -7255,7 +7346,7 @@
         "h": 7,
         "w": 8,
         "x": 0,
-        "y": 116
+        "y": 115
       },
       "id": 4,
       "options": {
@@ -7332,8 +7423,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -7349,7 +7439,7 @@
         "h": 7,
         "w": 8,
         "x": 8,
-        "y": 116
+        "y": 115
       },
       "id": 42,
       "options": {
@@ -7427,8 +7517,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -7444,7 +7533,7 @@
         "h": 7,
         "w": 8,
         "x": 16,
-        "y": 116
+        "y": 115
       },
       "id": 83,
       "options": {
@@ -7522,8 +7611,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -7539,7 +7627,7 @@
         "h": 7,
         "w": 8,
         "x": 0,
-        "y": 123
+        "y": 122
       },
       "id": 2,
       "options": {
@@ -7616,8 +7704,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -7633,7 +7720,7 @@
         "h": 7,
         "w": 8,
         "x": 8,
-        "y": 123
+        "y": 122
       },
       "id": 43,
       "options": {
@@ -7710,8 +7797,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -7727,7 +7813,7 @@
         "h": 7,
         "w": 8,
         "x": 16,
-        "y": 123
+        "y": 122
       },
       "id": 82,
       "options": {
@@ -7805,8 +7891,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -7822,7 +7907,7 @@
         "h": 7,
         "w": 8,
         "x": 0,
-        "y": 130
+        "y": 129
       },
       "id": 122,
       "options": {
@@ -7900,8 +7985,7 @@
             "mode": "absolute",
             "steps": [
               {
-                "color": "green",
-                "value": null
+                "color": "green"
               },
               {
                 "color": "red",
@@ -7917,7 +8001,7 @@
         "h": 7,
         "w": 8,
         "x": 8,
-        "y": 130
+        "y": 129
       },
       "id": 210,
       "options": {
@@ -7985,7 +8069,7 @@
           "type": "prometheus",
           "uid": "${DS_PROMETHEUS}"
         },
-        "definition": "label_values(blaze_db_cache_hits_total, job)",
+        "definition": "label_values(blaze_cache_hits_total, job)",
         "hide": 0,
         "includeAll": false,
         "label": "Job",
@@ -7993,7 +8077,7 @@
         "name": "job",
         "options": [],
         "query": {
-          "query": "label_values(blaze_db_cache_hits_total, job)",
+          "query": "label_values(blaze_cache_hits_total, job)",
           "refId": "StandardVariableQuery"
         },
         "refresh": 1,
@@ -8012,14 +8096,14 @@
           "type": "prometheus",
           "uid": "${DS_PROMETHEUS}"
         },
-        "definition": "label_values(blaze_db_cache_estimated_size{job=\"$job\"}, instance)",
+        "definition": "label_values(blaze_cache_estimated_size{job=\"$job\"}, instance)",
         "hide": 0,
         "includeAll": false,
         "multi": false,
         "name": "instance",
         "options": [],
         "query": {
-          "query": "label_values(blaze_db_cache_estimated_size{job=\"$job\"}, instance)",
+          "query": "label_values(blaze_cache_estimated_size{job=\"$job\"}, instance)",
           "refId": "StandardVariableQuery"
         },
         "refresh": 1,
@@ -8129,6 +8213,6 @@
   "timezone": "",
   "title": "Blaze",
   "uid": "Q-h9isMWk",
-  "version": 1,
+  "version": 2,
   "weekStart": ""
 }
diff --git a/docs/performance/cql.md b/docs/performance/cql.md
index b2926fb8a..f72b49729 100644
--- a/docs/performance/cql.md
+++ b/docs/performance/cql.md
@@ -42,17 +42,19 @@ define InInitialPopulation:
 The CQL query is executed with the following `blazectl` command:
 
 ```sh
-blazectl evaluate-measure "cql/observation-$CODE.yml" --server http://localhost:8080/fhir | jq -rf cql/result.jq
+cql/search.sh observation-17861-6
+cql/search.sh observation-8310-5
+cql/search.sh observation-72514-3
 ```
 
 | System | Dataset | Code    | # Hits | Time (s) | StdDev |  Pat./s |
 |--------|---------|---------|-------:|---------:|-------:|--------:|
-| LEA47  | 100k    | 17861-6 |    2 k |     0.26 |  0.158 | 384.5 k | 
-| LEA47  | 100k    | 8310-5  |   60 k |     0.28 |  0.142 | 351.4 k | 
-| LEA47  | 100k    | 72514-3 |  100 k |     0.27 |  0.128 | 367.0 k |
-| LEA47  | 1M      | 17861-6 |   25 k |     2.61 |  0.208 | 383.1 k | 
-| LEA47  | 1M      | 8310-5  |  603 k |     2.68 |  0.201 | 372.8 k | 
-| LEA47  | 1M      | 72514-3 |  998 k |     2.82 |  0.192 | 354.9 k |
+| LEA47  | 100k    | 17861-6 |    2 k |     0.09 |  0.001 |   1.1 M | 
+| LEA47  | 100k    | 8310-5  |   60 k |     0.10 |  0.001 |   1.0 M | 
+| LEA47  | 100k    | 72514-3 |  100 k |     0.10 |  0.002 |   1.0 M |
+| LEA47  | 1M      | 17861-6 |   25 k |     0.96 |  0.006 |   1.0 M |  
+| LEA47  | 1M      | 8310-5  |  603 k |     0.99 |  0.008 |   1.0 M | 
+| LEA47  | 1M      | 72514-3 |  998 k |     1.02 |  0.005 | 980.5 k |
 | LEA58  | 1M      | 17861-6 |   25 k |     2.87 |  0.291 | 348.5 k |
 | LEA58  | 1M      | 8310-5  |  603 k |     3.02 |  0.257 | 330.8 k | 
 | LEA58  | 1M      | 72514-3 |  998 k |     3.06 |  0.426 | 326.7 k |
@@ -80,22 +82,24 @@ define InInitialPopulation:
 The CQL query is executed with the following `blazectl` command:
 
 ```sh
-blazectl evaluate-measure "cql/observation-$CODE-$VALUE.yml" --server http://localhost:8080/fhir | jq -rf cql/result.jq
+cql/search.sh observation-body-weight-10
+cql/search.sh observation-body-weight-50
+cql/search.sh observation-body-weight-100
 ```
 
 | System | Dataset | Code    |   Value | # Hits | Time (s) | StdDev |  Pat./s |
 |--------|---------|---------|--------:|-------:|---------:|-------:|--------:|
-| LEA47  | 100k    | 29463-7 | 13.6 kg |   10 k |     0.68 |  0.031 | 146.9 k | 
-| LEA47  | 100k    | 29463-7 | 75.3 kg |   50 k |     0.51 |  0.033 | 197.1 k | 
-| LEA47  | 100k    | 29463-7 |  185 kg |  100 k |     0.30 |  0.106 | 331.6 k |
-| LEA47  | 1M      | 29463-7 | 13.6 kg |   99 k |   151.05 |  4.674 |   6.6 k | 
-| LEA47  | 1M      | 29463-7 | 75.3 kg |  500 k |   104.68 |  2.022 |   9.6 k | 
-| LEA47  | 1M      | 29463-7 |  185 kg |  998 k |     3.19 |  0.176 | 313.8 k |
+| LEA47  | 100k    | 29463-7 | 13.6 kg |   10 k |     0.09 |  0.001 |   1.1 M | 
+| LEA47  | 100k    | 29463-7 | 75.3 kg |   50 k |     0.10 |  0.001 |   1.0 M | 
+| LEA47  | 100k    | 29463-7 |  185 kg |  100 k |     0.10 |  0.001 |   1.0 M |
+| LEA47  | 1M      | 29463-7 | 13.6 kg |   99 k |     0.98 |  0.013 |   1.0 M | 
+| LEA47  | 1M      | 29463-7 | 75.3 kg |  500 k |     1.03 |  0.014 | 966.4 k | 
+| LEA47  | 1M      | 29463-7 |  185 kg |  998 k |     1.03 |  0.007 | 970.5 k |
 | LEA58  | 1M      | 29463-7 | 13.6 kg |   99 k |     8.24 |  0.072 | 121.4 k | 
 | LEA58  | 1M      | 29463-7 | 75.3 kg |  500 k |     6.59 |  0.140 | 151.8 k | 
 | LEA58  | 1M      | 29463-7 |  185 kg |  998 k |     3.04 |  0.209 | 329.0 k |
 
-## Code and Value Search
+## Code, Date and Age Search
 
 In this section, CQL Queries for selecting Patients which have Observation resources with code 718-7 (Hemoglobin), date between 2015 and 2019 and age of patient at observation date below 18.
 
@@ -110,21 +114,117 @@ context Patient
 
 define InInitialPopulation:
   exists [Observation: Code '718-7' from loinc] O
-  where year from O.effective between 2015 and 2019
-  and AgeInYearsAt(O.effective) < 18
+  where year from (O.effective as dateTime) between 2015 and 2019
+  and AgeInYearsAt(O.effective as dateTime) < 18
 ```
 
 The CQL query is executed with the following `blazectl` command:
 
 ```sh
-blazectl evaluate-measure "cql/hemoglobin-date-age.yml" --server http://localhost:8080/fhir | jq -rf cql/result.jq
+cql/search.sh hemoglobin-date-age
+cql/search.sh calcium-date-age
 ```
 
 | System | Dataset | Code       | # Hits | Time (s) | StdDev |  Pat./s |
 |--------|---------|------------|-------:|---------:|-------:|--------:|
-| LEA47  | 100k    | hemoglobin |   20 k |     0.35 |  0.034 | 286.5 k |
-| LEA47  | 100k    | calcium    |   20 k |     1.50 |  0.035 |  66.6 k |
-| LEA47  | 1M      | hemoglobin |  200 k |     4.79 |  0.119 | 208.8 k |
-| LEA47  | 1M      | calcium    |  199 k |   182.90 |  3.900 |   5.5 k |
+| LEA47  | 100k    | hemoglobin |   20 k |     0.09 |  0.001 |   1.1 M |
+| LEA47  | 100k    | calcium    |   20 k |     0.09 |  0.001 |   1.1 M |
+| LEA47  | 1M      | hemoglobin |  200 k |     1.01 |  0.018 | 989.7 k |
+| LEA47  | 1M      | calcium    |  199 k |     0.99 |  0.015 |   1.0 M |
 | LEA58  | 1M      | hemoglobin |  200 k |     3.55 |  0.038 | 281.8 k |
 | LEA58  | 1M      | calcium    |  199 k |    10.10 |  0.033 |  99.0 k |
+
+## Double Code Search
+
+In this section, CQL Queries for selecting Patients which have Condition resources with one of two codes used.
+
+```text
+library "condition-two"
+using FHIR version '4.0.0'
+include FHIRHelpers version '4.0.0'
+
+codesystem sct: 'http://snomed.info/sct'
+code fever: '386661006' from sct
+code cough: '49727002' from sct
+
+context Patient
+
+define InInitialPopulation:
+  exists [Condition: fever] or 
+  exists [Condition: cough]
+```
+
+```sh
+cql/search.sh condition-two
+```
+
+| System | Dataset | # Hits | Time (s) | StdDev |  Pat./s |
+|--------|---------|-------:|---------:|-------:|--------:|
+| LEA47  | 100k    |    9 k |     0.10 |  0.002 | 988.5 k |
+| LEA47  | 1M      |   87 k |     1.01 |  0.010 | 988.8 k |
+
+## Ten Frequent Code Search
+
+```text
+library "condition-ten-frequent"
+using FHIR version '4.0.0'
+include FHIRHelpers version '4.0.0'
+
+codesystem sct: 'http://snomed.info/sct'
+
+context Patient
+
+define InInitialPopulation:
+  exists [Condition: Code '444814009' from sct] or
+  exists [Condition: Code '840544004' from sct] or
+  exists [Condition: Code '840539006' from sct] or
+  exists [Condition: Code '386661006' from sct] or
+  exists [Condition: Code '195662009' from sct] or
+  exists [Condition: Code '49727002' from sct] or
+  exists [Condition: Code '10509002' from sct] or
+  exists [Condition: Code '72892002' from sct] or
+  exists [Condition: Code '36955009' from sct] or
+  exists [Condition: Code '162864005' from sct]
+```
+
+```sh
+cql/search.sh condition-ten-frequent
+```
+
+| System | Dataset | # Hits | Time (s) | StdDev |  Pat./s |
+|--------|---------|-------:|---------:|-------:|--------:|
+| LEA47  | 100k    |   95 k |     0.11 |  0.003 | 899.0 k |
+| LEA47  | 1M      |  954 k |     1.14 |  0.014 | 880.7 k |
+
+## Ten Rare Code Search
+
+```text
+library "condition-ten-rare"
+using FHIR version '4.0.0'
+include FHIRHelpers version '4.0.0'
+
+codesystem sct: 'http://snomed.info/sct'
+
+context Patient
+
+define InInitialPopulation:
+  exists [Condition: Code '62718007' from sct] or
+  exists [Condition: Code '234466008' from sct] or
+  exists [Condition: Code '288959006' from sct] or
+  exists [Condition: Code '47505003' from sct] or
+  exists [Condition: Code '698754002' from sct] or
+  exists [Condition: Code '157265008' from sct] or
+  exists [Condition: Code '15802004' from sct] or
+  exists [Condition: Code '14760008' from sct] or
+  exists [Condition: Code '36923009' from sct] or
+  exists [Condition: Code '45816000' from sct]
+```
+
+```sh
+cql/search.sh condition-ten-rare
+```
+
+| System | Dataset | # Hits | Time (s) | StdDev |  Pat./s |
+|--------|---------|-------:|---------:|-------:|--------:|
+| LEA47  | 100k    |    0 k |     0.14 |  0.002 | 726.0 k |
+| LEA47  | 1M      |    4 k |     1.59 |  0.016 | 627.1 k |
diff --git a/docs/performance/cql/calcium-date-age.cql b/docs/performance/cql/calcium-date-age.cql
index 30fb87733..4dcc668a7 100644
--- a/docs/performance/cql/calcium-date-age.cql
+++ b/docs/performance/cql/calcium-date-age.cql
@@ -8,5 +8,5 @@ context Patient
 
 define InInitialPopulation:
   exists [Observation: Code '49765-1' from loinc] O
-  where year from O.effective between 2015 and 2019
-  and AgeInYearsAt(O.effective) < 59
+  where year from (O.effective as dateTime as dateTime) between 2015 and 2019
+  and AgeInYearsAt(O.effective as dateTime) < 59
diff --git a/docs/performance/cql/code-date-age-search.sh b/docs/performance/cql/code-date-age-search.sh
deleted file mode 100755
index 0470f1017..000000000
--- a/docs/performance/cql/code-date-age-search.sh
+++ /dev/null
@@ -1,22 +0,0 @@
-#!/bin/bash -e
-
-SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
-. "$SCRIPT_DIR/util.sh"
-
-BASE="http://localhost:8080/fhir"
-START_EPOCH="$(date +"%s")"
-PATIENT_TOTAL="$(curl -sH 'Accept: application/fhir+json' "$BASE/Patient?_summary=count" | jq -r .total)"
-CODE="$1"
-
-echo "Counting Patients with Observations with code $CODE, date between 2015 and 2019 and age of patient at observation date below 18..."
-
-MEASURE_FILE="$SCRIPT_DIR/$CODE-date-age.yml"
-TIMES_FILE="$START_EPOCH-$CODE-date-age.times"
-COUNT="$(blazectl --server "$BASE" evaluate-measure "$MEASURE_FILE" 2> /dev/null | jq -r '.group[0].population[0].count')"
-
-for i in {0..6}
-do
-  blazectl --server "$BASE" evaluate-measure "$MEASURE_FILE" 2> /dev/null |\
-    jq -rf "$SCRIPT_DIR/duration.jq" >> "$TIMES_FILE"
-done
-calc-cql-print-stats "$TIMES_FILE" "$PATIENT_TOTAL" "$COUNT"
diff --git a/docs/performance/cql/code-value-search.sh b/docs/performance/cql/code-value-search.sh
deleted file mode 100755
index 2126191c3..000000000
--- a/docs/performance/cql/code-value-search.sh
+++ /dev/null
@@ -1,19 +0,0 @@
-#!/bin/bash -e
-
-SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
-. "$SCRIPT_DIR/util.sh"
-
-BASE="http://localhost:8080/fhir"
-START_EPOCH="$(date +"%s")"
-PATIENT_TOTAL="$(curl -sH 'Accept: application/fhir+json' "$BASE/Patient?_summary=count" | jq -r .total)"
-CODE="$1"
-VALUE="$2"
-
-echo "Counting Patients with Observations with code $CODE and value $VALUE..."
-COUNT="$(blazectl --server "$BASE" evaluate-measure "$SCRIPT_DIR/observation-$CODE-$VALUE.yml" 2> /dev/null | jq -r '.group[0].population[0].count')"
-for i in {0..6}
-do
-  blazectl evaluate-measure "cql/observation-$CODE-$VALUE.yml" --server "$BASE" 2> /dev/null |\
-    jq -rf cql/duration.jq >> "$START_EPOCH-$CODE-$VALUE.times"
-done
-calc-cql-print-stats "$START_EPOCH-$CODE-$VALUE.times" "$PATIENT_TOTAL" "$COUNT"
diff --git a/docs/performance/cql/condition-all.cql b/docs/performance/cql/condition-all.cql
new file mode 100644
index 000000000..3763238e0
--- /dev/null
+++ b/docs/performance/cql/condition-all.cql
@@ -0,0 +1,228 @@
+library "condition-all"
+using FHIR version '4.0.0'
+include FHIRHelpers version '4.0.0'
+
+codesystem sct: 'http://snomed.info/sct'
+
+context Patient
+
+define InInitialPopulation:
+  exists [Condition: Code '234466008' from sct] or
+  exists [Condition: Code '65275009' from sct] or
+  exists [Condition: Code '241929008' from sct] or
+  exists [Condition: Code '75498004' from sct] or
+  exists [Condition: Code '10509002' from sct] or
+  exists [Condition: Code '132281000119108' from sct] or
+  exists [Condition: Code '706870000' from sct] or
+  exists [Condition: Code '67782005' from sct] or
+  exists [Condition: Code '65710008' from sct] or
+  exists [Condition: Code '195662009' from sct] or
+  exists [Condition: Code '7200002' from sct] or
+  exists [Condition: Code '300916003' from sct] or
+  exists [Condition: Code '26929004' from sct] or
+  exists [Condition: Code '271737000' from sct] or
+  exists [Condition: Code '198992004' from sct] or
+  exists [Condition: Code '74400008' from sct] or
+  exists [Condition: Code '195967001' from sct] or
+  exists [Condition: Code '225444004' from sct] or
+  exists [Condition: Code '24079001' from sct] or
+  exists [Condition: Code '49436004' from sct] or
+  exists [Condition: Code '287185009' from sct] or
+  exists [Condition: Code '87628006' from sct] or
+  exists [Condition: Code '6072007' from sct] or
+  exists [Condition: Code '35999006' from sct] or
+  exists [Condition: Code '60951000119105' from sct] or
+  exists [Condition: Code '162864005' from sct] or
+  exists [Condition: Code '408512008' from sct] or
+  exists [Condition: Code '275272006' from sct] or
+  exists [Condition: Code '262574004' from sct] or
+  exists [Condition: Code '840539006' from sct] or
+  exists [Condition: Code '92691004' from sct] or
+  exists [Condition: Code '410429000' from sct] or
+  exists [Condition: Code '128188000' from sct] or
+  exists [Condition: Code '373587001' from sct] or
+  exists [Condition: Code '192127007' from sct] or
+  exists [Condition: Code '233678006' from sct] or
+  exists [Condition: Code '43724002' from sct] or
+  exists [Condition: Code '235919008' from sct] or
+  exists [Condition: Code '88805009' from sct] or
+  exists [Condition: Code '124171000119105' from sct] or
+  exists [Condition: Code '431855005' from sct] or
+  exists [Condition: Code '431856006' from sct] or
+  exists [Condition: Code '433144002' from sct] or
+  exists [Condition: Code '278860009' from sct] or
+  exists [Condition: Code '1121000119107' from sct] or
+  exists [Condition: Code '185086009' from sct] or
+  exists [Condition: Code '82423001' from sct] or
+  exists [Condition: Code '698754002' from sct] or
+  exists [Condition: Code '40055000' from sct] or
+  exists [Condition: Code '359817006' from sct] or
+  exists [Condition: Code '110030002' from sct] or
+  exists [Condition: Code '62564004' from sct] or
+  exists [Condition: Code '62106007' from sct] or
+  exists [Condition: Code '302297009' from sct] or
+  exists [Condition: Code '14760008' from sct] or
+  exists [Condition: Code '40275004' from sct] or
+  exists [Condition: Code '53741008' from sct] or
+  exists [Condition: Code '49727002' from sct] or
+  exists [Condition: Code '190905008' from sct] or
+  exists [Condition: Code '38822007' from sct] or
+  exists [Condition: Code '44054006' from sct] or
+  exists [Condition: Code '427089005' from sct] or
+  exists [Condition: Code '127013003' from sct] or
+  exists [Condition: Code '422034002' from sct] or
+  exists [Condition: Code '267060006' from sct] or
+  exists [Condition: Code '157265008' from sct] or
+  exists [Condition: Code '62718007' from sct] or
+  exists [Condition: Code '55680006' from sct] or
+  exists [Condition: Code '55680006' from sct] or
+  exists [Condition: Code '267036007' from sct] or
+  exists [Condition: Code '15802004' from sct] or
+  exists [Condition: Code '84757009' from sct] or
+  exists [Condition: Code '84757009' from sct] or
+  exists [Condition: Code '301011002' from sct] or
+  exists [Condition: Code '53827007' from sct] or
+  exists [Condition: Code '370247008' from sct] or
+  exists [Condition: Code '230265002' from sct] or
+  exists [Condition: Code '84229001' from sct] or
+  exists [Condition: Code '707577004' from sct] or
+  exists [Condition: Code '156073000' from sct] or
+  exists [Condition: Code '386661006' from sct] or
+  exists [Condition: Code '203082005' from sct] or
+  exists [Condition: Code '403190006' from sct] or
+  exists [Condition: Code '16114001' from sct] or
+  exists [Condition: Code '58150001' from sct] or
+  exists [Condition: Code '65966004' from sct] or
+  exists [Condition: Code '33737001' from sct] or
+  exists [Condition: Code '1734006' from sct] or
+  exists [Condition: Code '15724005' from sct] or
+  exists [Condition: Code '263102004' from sct] or
+  exists [Condition: Code '235595009' from sct] or
+  exists [Condition: Code '90560007' from sct] or
+  exists [Condition: Code '25064002' from sct] or
+  exists [Condition: Code '84114007' from sct] or
+  exists [Condition: Code '66857006' from sct] or
+  exists [Condition: Code '429280009' from sct] or
+  exists [Condition: Code '428251008' from sct] or
+  exists [Condition: Code '429007001' from sct] or
+  exists [Condition: Code '161622006' from sct] or
+  exists [Condition: Code '399211009' from sct] or
+  exists [Condition: Code '703151001' from sct] or
+  exists [Condition: Code '230745008' from sct] or
+  exists [Condition: Code '80394007' from sct] or
+  exists [Condition: Code '55822004' from sct] or
+  exists [Condition: Code '59621000' from sct] or
+  exists [Condition: Code '302870006' from sct] or
+  exists [Condition: Code '389087006' from sct] or
+  exists [Condition: Code '83664006' from sct] or
+  exists [Condition: Code '196416002' from sct] or
+  exists [Condition: Code '11218009' from sct] or
+  exists [Condition: Code '406602003' from sct] or
+  exists [Condition: Code '444470001' from sct] or
+  exists [Condition: Code '86175003' from sct] or
+  exists [Condition: Code '40095003' from sct] or
+  exists [Condition: Code '444448004' from sct] or
+  exists [Condition: Code '307731004' from sct] or
+  exists [Condition: Code '110359009' from sct] or
+  exists [Condition: Code '57676002' from sct] or
+  exists [Condition: Code '414564002' from sct] or
+  exists [Condition: Code '284551006' from sct] or
+  exists [Condition: Code '283371005' from sct] or
+  exists [Condition: Code '284549007' from sct] or
+  exists [Condition: Code '283385000' from sct] or
+  exists [Condition: Code '201834006' from sct] or
+  exists [Condition: Code '36955009' from sct] or
+  exists [Condition: Code '200936003' from sct] or
+  exists [Condition: Code '97331000119101' from sct] or
+  exists [Condition: Code '370143000' from sct] or
+  exists [Condition: Code '36923009' from sct] or
+  exists [Condition: Code '427089005' from sct] or
+  exists [Condition: Code '254837009' from sct] or
+  exists [Condition: Code '363406005' from sct] or
+  exists [Condition: Code '171131006' from sct] or
+  exists [Condition: Code '414667000' from sct] or
+  exists [Condition: Code '237602007' from sct] or
+  exists [Condition: Code '314994000' from sct] or
+  exists [Condition: Code '90781000119102' from sct] or
+  exists [Condition: Code '19169002' from sct] or
+  exists [Condition: Code '68962001' from sct] or
+  exists [Condition: Code '22298006' from sct] or
+  exists [Condition: Code '68235000' from sct] or
+  exists [Condition: Code '422587007' from sct] or
+  exists [Condition: Code '126906006' from sct] or
+  exists [Condition: Code '368581000119106' from sct] or
+  exists [Condition: Code '47200007' from sct] or
+  exists [Condition: Code '424132000' from sct] or
+  exists [Condition: Code '254637007' from sct] or
+  exists [Condition: Code '1551000119108' from sct] or
+  exists [Condition: Code '72892002' from sct] or
+  exists [Condition: Code '5602001' from sct] or
+  exists [Condition: Code '239872002' from sct] or
+  exists [Condition: Code '239873007' from sct] or
+  exists [Condition: Code '64859006' from sct] or
+  exists [Condition: Code '65363002' from sct] or
+  exists [Condition: Code '109838007' from sct] or
+  exists [Condition: Code '22253000' from sct] or
+  exists [Condition: Code '246677007' from sct] or
+  exists [Condition: Code '443165006' from sct] or
+  exists [Condition: Code '446096008' from sct] or
+  exists [Condition: Code '232353008' from sct] or
+  exists [Condition: Code '233604007' from sct] or
+  exists [Condition: Code '233604007' from sct] or
+  exists [Condition: Code '68496003' from sct] or
+  exists [Condition: Code '398152000' from sct] or
+  exists [Condition: Code '47505003' from sct] or
+  exists [Condition: Code '15777000' from sct] or
+  exists [Condition: Code '398254007' from sct] or
+  exists [Condition: Code '399912005' from sct] or
+  exists [Condition: Code '95417003' from sct] or
+  exists [Condition: Code '93761005' from sct] or
+  exists [Condition: Code '67811000119102' from sct] or
+  exists [Condition: Code '1501000119109' from sct] or
+  exists [Condition: Code '157141000119108' from sct] or
+  exists [Condition: Code '236077008' from sct] or
+  exists [Condition: Code '87433001' from sct] or
+  exists [Condition: Code '45816000' from sct] or
+  exists [Condition: Code '713197008' from sct] or
+  exists [Condition: Code '197927001' from sct] or
+  exists [Condition: Code '271825005' from sct] or
+  exists [Condition: Code '267064002' from sct] or
+  exists [Condition: Code '69896004' from sct] or
+  exists [Condition: Code '47693006' from sct] or
+  exists [Condition: Code '30832001' from sct] or
+  exists [Condition: Code '298382003' from sct] or
+  exists [Condition: Code '367498001' from sct] or
+  exists [Condition: Code '403191005' from sct] or
+  exists [Condition: Code '94260004' from sct] or
+  exists [Condition: Code '128613002' from sct] or
+  exists [Condition: Code '91302008' from sct] or
+  exists [Condition: Code '448813005' from sct] or
+  exists [Condition: Code '448417001' from sct] or
+  exists [Condition: Code '770349000' from sct] or
+  exists [Condition: Code '76571007' from sct] or
+  exists [Condition: Code '27942005' from sct] or
+  exists [Condition: Code '36971009' from sct] or
+  exists [Condition: Code '254632001' from sct] or
+  exists [Condition: Code '449868002' from sct] or
+  exists [Condition: Code '267102003' from sct] or
+  exists [Condition: Code '221360009' from sct] or
+  exists [Condition: Code '76916001' from sct] or
+  exists [Condition: Code '44465007' from sct] or
+  exists [Condition: Code '70704007' from sct] or
+  exists [Condition: Code '248595008' from sct] or
+  exists [Condition: Code '43878008' from sct] or
+  exists [Condition: Code '230690007' from sct] or
+  exists [Condition: Code '86849004' from sct] or
+  exists [Condition: Code '840544004' from sct] or
+  exists [Condition: Code '162573006' from sct] or
+  exists [Condition: Code '239720000' from sct] or
+  exists [Condition: Code '403192003' from sct] or
+  exists [Condition: Code '427419006' from sct] or
+  exists [Condition: Code '127295002' from sct] or
+  exists [Condition: Code '79586000' from sct] or
+  exists [Condition: Code '288959006' from sct] or
+  exists [Condition: Code '68566005' from sct] or
+  exists [Condition: Code '444814009' from sct] or
+  exists [Condition: Code '249497008' from sct] or
+  exists [Condition: Code '56018004' from sct] or
+  exists [Condition: Code '39848009' from sct]
diff --git a/docs/performance/cql/condition-all.yml b/docs/performance/cql/condition-all.yml
new file mode 100644
index 000000000..c05260376
--- /dev/null
+++ b/docs/performance/cql/condition-all.yml
@@ -0,0 +1,5 @@
+library: cql/condition-all.cql
+group:
+- type: Patient
+  population:
+  - expression: InInitialPopulation
diff --git a/docs/performance/cql/condition-ten-frequent.cql b/docs/performance/cql/condition-ten-frequent.cql
new file mode 100644
index 000000000..21f54cc03
--- /dev/null
+++ b/docs/performance/cql/condition-ten-frequent.cql
@@ -0,0 +1,19 @@
+library "condition-ten-frequent"
+using FHIR version '4.0.0'
+include FHIRHelpers version '4.0.0'
+
+codesystem sct: 'http://snomed.info/sct'
+
+context Patient
+
+define InInitialPopulation:
+  exists [Condition: Code '444814009' from sct] or
+  exists [Condition: Code '840544004' from sct] or
+  exists [Condition: Code '840539006' from sct] or
+  exists [Condition: Code '386661006' from sct] or
+  exists [Condition: Code '195662009' from sct] or
+  exists [Condition: Code '49727002' from sct] or
+  exists [Condition: Code '10509002' from sct] or
+  exists [Condition: Code '72892002' from sct] or
+  exists [Condition: Code '36955009' from sct] or
+  exists [Condition: Code '162864005' from sct]
diff --git a/docs/performance/cql/condition-ten-frequent.yml b/docs/performance/cql/condition-ten-frequent.yml
new file mode 100644
index 000000000..c98e4b241
--- /dev/null
+++ b/docs/performance/cql/condition-ten-frequent.yml
@@ -0,0 +1,5 @@
+library: cql/condition-ten-frequent.cql
+group:
+- type: Patient
+  population:
+  - expression: InInitialPopulation
diff --git a/docs/performance/cql/condition-ten-rare.cql b/docs/performance/cql/condition-ten-rare.cql
new file mode 100644
index 000000000..4c94ed068
--- /dev/null
+++ b/docs/performance/cql/condition-ten-rare.cql
@@ -0,0 +1,19 @@
+library "condition-ten-rare"
+using FHIR version '4.0.0'
+include FHIRHelpers version '4.0.0'
+
+codesystem sct: 'http://snomed.info/sct'
+
+context Patient
+
+define InInitialPopulation:
+  exists [Condition: Code '62718007' from sct] or
+  exists [Condition: Code '234466008' from sct] or
+  exists [Condition: Code '288959006' from sct] or
+  exists [Condition: Code '47505003' from sct] or
+  exists [Condition: Code '698754002' from sct] or
+  exists [Condition: Code '157265008' from sct] or
+  exists [Condition: Code '15802004' from sct] or
+  exists [Condition: Code '14760008' from sct] or
+  exists [Condition: Code '36923009' from sct] or
+  exists [Condition: Code '45816000' from sct]
diff --git a/docs/performance/cql/condition-ten-rare.yml b/docs/performance/cql/condition-ten-rare.yml
new file mode 100644
index 000000000..09ce1c85d
--- /dev/null
+++ b/docs/performance/cql/condition-ten-rare.yml
@@ -0,0 +1,5 @@
+library: cql/condition-ten-rare.cql
+group:
+- type: Patient
+  population:
+  - expression: InInitialPopulation
diff --git a/docs/performance/cql/condition-two.cql b/docs/performance/cql/condition-two.cql
new file mode 100644
index 000000000..36630e504
--- /dev/null
+++ b/docs/performance/cql/condition-two.cql
@@ -0,0 +1,13 @@
+library "condition-two"
+using FHIR version '4.0.0'
+include FHIRHelpers version '4.0.0'
+
+codesystem sct: 'http://snomed.info/sct'
+code fever: '386661006' from sct
+code cough: '49727002' from sct
+
+context Patient
+
+define InInitialPopulation:
+  exists [Condition: fever] or
+  exists [Condition: cough]
diff --git a/docs/performance/cql/condition-two.yml b/docs/performance/cql/condition-two.yml
new file mode 100644
index 000000000..46c786903
--- /dev/null
+++ b/docs/performance/cql/condition-two.yml
@@ -0,0 +1,5 @@
+library: cql/condition-two.cql
+group:
+- type: Patient
+  population:
+  - expression: InInitialPopulation
diff --git a/docs/performance/cql/hemoglobin-date-age.cql b/docs/performance/cql/hemoglobin-date-age.cql
index 81c25492a..554add059 100644
--- a/docs/performance/cql/hemoglobin-date-age.cql
+++ b/docs/performance/cql/hemoglobin-date-age.cql
@@ -8,5 +8,5 @@ context Patient
 
 define InInitialPopulation:
   exists [Observation: Code '718-7' from loinc] O
-  where year from O.effective between 2015 and 2019
-  and AgeInYearsAt(O.effective) < 18
+  where year from (O.effective as dateTime as dateTime) between 2015 and 2019
+  and AgeInYearsAt(O.effective as dateTime) < 18
diff --git a/docs/performance/cql/search.sh b/docs/performance/cql/search.sh
new file mode 100755
index 000000000..4648a95e8
--- /dev/null
+++ b/docs/performance/cql/search.sh
@@ -0,0 +1,19 @@
+#!/bin/bash -e
+
+SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
+. "$SCRIPT_DIR/util.sh"
+
+BASE="http://localhost:8080/fhir"
+START_EPOCH="$(date +"%s")"
+PATIENT_TOTAL="$(curl -sH 'Accept: application/fhir+json' "$BASE/Patient?_summary=count" | jq -r .total)"
+FILE="$1"
+
+echo "Counting Patients with criteria from $FILE..."
+COUNT="$(blazectl --server "$BASE" evaluate-measure "$SCRIPT_DIR/$FILE.yml" 2> /dev/null | jq -r '.group[0].population[0].count')"
+for i in {0..6}
+do
+  blazectl --server "$BASE" evaluate-measure "$SCRIPT_DIR/$FILE.yml" 2> /dev/null |\
+    jq -rf "$SCRIPT_DIR/duration.jq" >> "$START_EPOCH-$FILE.times"
+done
+
+calc-cql-print-stats "$START_EPOCH-$FILE.times" "$PATIENT_TOTAL" "$COUNT"
diff --git a/docs/performance/cql/simple-code-search.sh b/docs/performance/cql/simple-code-search.sh
deleted file mode 100755
index e59cea0e6..000000000
--- a/docs/performance/cql/simple-code-search.sh
+++ /dev/null
@@ -1,19 +0,0 @@
-#!/bin/bash -e
-
-SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
-. "$SCRIPT_DIR/util.sh"
-
-BASE="http://localhost:8080/fhir"
-START_EPOCH="$(date +"%s")"
-PATIENT_TOTAL="$(curl -sH 'Accept: application/fhir+json' "$BASE/Patient?_summary=count" | jq -r .total)"
-CODE="$1"
-
-echo "Counting Patients with Observations with code $CODE..."
-COUNT="$(blazectl --server "$BASE" evaluate-measure "$SCRIPT_DIR/observation-$CODE.yml" 2> /dev/null | jq -r '.group[0].population[0].count')"
-for i in {0..6}
-do
-  blazectl --server "$BASE" evaluate-measure "$SCRIPT_DIR/observation-$CODE.yml" 2> /dev/null |\
-    jq -rf "$SCRIPT_DIR/duration.jq" >> "$START_EPOCH-$CODE.times"
-done
-
-calc-cql-print-stats "$START_EPOCH-$CODE.times" "$PATIENT_TOTAL" "$COUNT"
diff --git a/docs/performance/cql/util.sh b/docs/performance/cql/util.sh
index 6f84918b9..3a9f2825e 100644
--- a/docs/performance/cql/util.sh
+++ b/docs/performance/cql/util.sh
@@ -24,7 +24,10 @@ calc-cql-print-stats() {
   fi
 
   # shorten the patients per second
-  if (( $(echo "$PATIENTS_PER_SEC > 1000" | bc) )); then
+  if (( $(echo "$PATIENTS_PER_SEC > 1000000" | bc) )); then
+    PATIENTS_PER_SEC=$(echo "scale=2; $PATIENTS_PER_SEC / 1000000" | bc)
+    PATIENTS_PER_SEC_FORMAT="%4.1f M"
+  elif (( $(echo "$PATIENTS_PER_SEC > 1000" | bc) )); then
     PATIENTS_PER_SEC=$(echo "scale=2; $PATIENTS_PER_SEC / 1000" | bc)
     PATIENTS_PER_SEC_FORMAT="%4.1f k"
   else
diff --git a/docs/performance/synthea/README.md b/docs/performance/synthea/README.md
index cc5c421c0..01699ca52 100644
--- a/docs/performance/synthea/README.md
+++ b/docs/performance/synthea/README.md
@@ -14,8 +14,10 @@ docker run -v "$(pwd)/output:/gen/output" synthea 100
 
 ## Post-Process Bundles
 
+While Synthea is running, it's important to run alrady the post-process loop. Otherwise the amount of data Synthea generates will likely fill your disk with uncompressed FHIR bundles. 
+
 ```sh
-./post-process-bundles.sh output/fhir
+./post-process-bundle-loop.sh output/fhir
 ```
 
 ## Upload Bundles 
diff --git a/modules/admin-api/.clj-kondo/config.edn b/modules/admin-api/.clj-kondo/config.edn
index b588017ea..b25e046ab 100644
--- a/modules/admin-api/.clj-kondo/config.edn
+++ b/modules/admin-api/.clj-kondo/config.edn
@@ -1,5 +1,6 @@
 {:lint-as
- {blaze.admin-api-test/with-handler clojure.core/fn}
+ {blaze.admin-api-test/with-handler clojure.core/fn
+  blaze.anomaly/if-ok clojure.core/let}
 
  :linters
  {:unsorted-required-namespaces
diff --git a/modules/admin-api/deps.edn b/modules/admin-api/deps.edn
index e20aadb66..8c780c24b 100644
--- a/modules/admin-api/deps.edn
+++ b/modules/admin-api/deps.edn
@@ -12,7 +12,10 @@
   {:local/root "../rocksdb"}
 
   blaze/spec
-  {:local/root "../spec"}}
+  {:local/root "../spec"}
+
+  fi.metosin/reitit-openapi
+  {:mvn/version "0.7.0-alpha5"}}
 
  :aliases
  {:test
diff --git a/modules/admin-api/src/blaze/admin_api.clj b/modules/admin-api/src/blaze/admin_api.clj
index f99e365c3..d82519491 100644
--- a/modules/admin-api/src/blaze/admin_api.clj
+++ b/modules/admin-api/src/blaze/admin_api.clj
@@ -1,10 +1,13 @@
 (ns blaze.admin-api
   (:require
+    [blaze.anomaly :refer [if-ok]]
     [blaze.async.comp :as ac]
+    [blaze.db.impl.index.patient-as-of :as pao]
     [blaze.db.kv.rocksdb :as rocksdb]
     [blaze.spec]
     [clojure.spec.alpha :as s]
     [integrant.core :as ig]
+    [reitit.openapi :as openapi]
     [reitit.ring]
     [reitit.ring.spec]
     [ring.util.response :as ring]
@@ -18,26 +21,86 @@
         (ac/completed-future))))
 
 
-(defn- rocksdb-table-handler [index-kv-store]
+(defn- cf-state-handler [index-kv-store]
   (fn [{{:keys [column-family]} :path-params}]
-    (-> (ring/response {:tables (rocksdb/table-properties index-kv-store (keyword column-family))})
+    (-> (if (= "patient-as-of-index" column-family)
+          (ring/response (pao/state index-kv-store))
+          (ring/not-found {:msg (format "The column family `%s` has no state." column-family)}))
         (ac/completed-future))))
 
 
+(defn- cf-rocksdb-table-handler [index-kv-store]
+  (fn [{{:keys [column-family]} :path-params}]
+    (-> (if-ok [tables (rocksdb/table-properties index-kv-store (keyword column-family))]
+          (ring/response {:tables tables})
+          (fn [_] (ring/not-found {:msg (format "The column family `%s` was not found." column-family)})))
+        (ac/completed-future))))
+
+
+(def ^:private openapi-handler
+  (let [handler (openapi/create-openapi-handler)]
+    (fn [request]
+      (ac/completed-future (handler request)))))
+
+
 (defn- router [{:keys [context-path index-kv-store] :or {context-path ""}}]
   (reitit.ring/router
-    ["/rocksdb"
-     {}
-     ["/index"
+    [""
+     {:openapi {:id :admin-api}
+      :middleware [openapi/openapi-feature]}
+     ["/openapi.json"
+      {:get {:handler openapi-handler
+             :openapi {:info {:title "Blaze Admin API" :version "0.22"}}
+             :no-doc true}}]
+     ["/db"
       {}
-      ["/column-families"
+      ["/index"
        {}
-       [""
-        {:get (rocksdb-column-families-handler index-kv-store)}]
-       ["/{column-family}"
+       ["/column-families"
         {}
-        ["/tables"
-         {:get (rocksdb-table-handler index-kv-store)}]]]]]
+        [""
+         {:get
+          {:handler (rocksdb-column-families-handler index-kv-store)
+           :summary "Fetch a list of all column families."
+           :openapi
+           {:responses
+            {200
+             {:content
+              {"application/json"
+               {:schema
+                {:type "object"
+                 :properties
+                 [:column-families
+                  {:type "array"
+                   :items {:type "string"}}]}}}}}}}}]
+        ["/{column-family}"
+         {}
+         ["/state"
+          {:get
+           {:handler (cf-state-handler index-kv-store)}}]
+         ["/rocksdb-tables"
+          {:get
+           {:handler (cf-rocksdb-table-handler index-kv-store)
+            :summary "Fetch a list of all tables of a column family."
+            :openapi
+            {:parameters
+             [{:name "column-family"
+               :in "path"
+               :required true}]
+             :responses
+             {200
+              {:content
+               {"application/json"
+                {:schema
+                 {:type "object"
+                  :properties
+                  [:tables
+                   {:type "array"
+                    :items
+                    {:type "object"
+                     :properties
+                     [:data-size {:type "integer"}
+                      :total-raw-key-size {:type "integer"}]}}]}}}}}}}}]]]]]]
     {:path (str context-path "/__admin")
      :syntax :bracket}))
 
diff --git a/modules/admin-api/test/blaze/admin_api_test.clj b/modules/admin-api/test/blaze/admin_api_test.clj
index f538d8207..383770d65 100644
--- a/modules/admin-api/test/blaze/admin_api_test.clj
+++ b/modules/admin-api/test/blaze/admin_api_test.clj
@@ -1,6 +1,8 @@
 (ns blaze.admin-api-test
   (:require
     [blaze.admin-api]
+    [blaze.anomaly :as ba]
+    [blaze.db.impl.index.patient-as-of :as pao]
     [blaze.db.kv.rocksdb.protocols :as p]
     [blaze.module.test-util :refer [with-system]]
     [blaze.test-util :as tu :refer [given-thrown]]
@@ -47,9 +49,10 @@
       (keys column-families))
 
     (-table-properties [_ column-family]
-      (when (column-families column-family)
+      (if (column-families column-family)
         [{:name (str (name column-family) "/table-1")
-          :data-size 193338}]))))
+          :data-size 193338}]
+        (ba/not-found "")))))
 
 
 (def config
@@ -69,28 +72,55 @@
        ~@body)))
 
 
-(deftest rocksdb-column-families-test
+(deftest handler-not-found-test
+  (with-handler [handler]
+    (given @(handler
+              {:request-method :get
+               :uri "/fhir/__admin/foo"})
+      :status := 404)))
+
+
+(deftest column-families-test
   (with-handler [handler]
     (testing "success"
       (given @(handler
                 {:request-method :get
-                 :uri "/fhir/__admin/rocksdb/index/column-families"})
+                 :uri "/fhir/__admin/db/index/column-families"})
         :status := 200
         [:body :column-families] := ["column-family-1" "column-family-2"]))))
 
 
-(deftest rocksdb-tables-test
+(deftest column-family-state-test
   (with-handler [handler]
-    (testing "not found"
+    (testing "patient-as-of-index"
+      (with-redefs [pao/state (fn [_] ::state)]
+        (given @(handler
+                  {:request-method :get
+                   :uri "/fhir/__admin/db/index/column-families/patient-as-of-index/state"})
+          :status := 200
+          :body := ::state)))
+
+    (testing "other column-family"
       (given @(handler
                 {:request-method :get
-                 :uri "/fhir/__admin/foo"})
-        :status := 404))
+                 :uri "/fhir/__admin/db/index/column-families/column-family-1/state"})
+        :status := 404
+        [:body :msg] := "The column family `column-family-1` has no state."))))
+
 
+(deftest rocksdb-tables-test
+  (with-handler [handler]
     (testing "success"
       (given @(handler
                 {:request-method :get
-                 :uri "/fhir/__admin/rocksdb/index/column-families/column-family-1/tables"})
+                 :uri "/fhir/__admin/db/index/column-families/column-family-1/rocksdb-tables"})
         :status := 200
         [:body :tables 0 :name] := "column-family-1/table-1"
-        [:body :tables 0 :data-size] := 193338))))
+        [:body :tables 0 :data-size] := 193338))
+
+    (testing "not-found"
+      (given @(handler
+                {:request-method :get
+                 :uri "/fhir/__admin/db/index/column-families/column-family-3/rocksdb-tables"})
+        :status := 404
+        [:body :msg] := "The column family `column-family-3` was not found."))))
diff --git a/modules/byte-buffer/src/blaze/byte_buffer.clj b/modules/byte-buffer/src/blaze/byte_buffer.clj
index b4e6b2348..de8f18577 100644
--- a/modules/byte-buffer/src/blaze/byte_buffer.clj
+++ b/modules/byte-buffer/src/blaze/byte_buffer.clj
@@ -225,10 +225,15 @@
 
 (defn get-long!
   {:inline
-   (fn [byte-buffer]
-     `(.getLong ~(vary-meta byte-buffer assoc :tag `ByteBuffer)))}
-  [byte-buffer]
-  (.getLong ^ByteBuffer byte-buffer))
+   (fn
+     ([byte-buffer]
+      `(.getLong ~(vary-meta byte-buffer assoc :tag `ByteBuffer)))
+     ([byte-buffer index]
+      `(.getLong ~(vary-meta byte-buffer assoc :tag `ByteBuffer) (int ~index))))}
+  ([byte-buffer]
+   (.getLong ^ByteBuffer byte-buffer))
+  ([byte-buffer index]
+   (.getLong ^ByteBuffer byte-buffer (int index))))
 
 
 (defn copy-into-byte-array!
diff --git a/modules/cache-collector/.clj-kondo/config.edn b/modules/cache-collector/.clj-kondo/config.edn
new file mode 100644
index 000000000..a25d19101
--- /dev/null
+++ b/modules/cache-collector/.clj-kondo/config.edn
@@ -0,0 +1,20 @@
+{:lint-as
+ {blaze.module.test-util/with-system clojure.core/with-open}
+
+ :linters
+ {:unsorted-required-namespaces
+  {:level :error}
+
+  :single-key-in
+  {:level :warning}
+
+  :keyword-binding
+  {:level :error}
+
+  :reduce-without-init
+  {:level :warning}
+
+  :warn-on-reflection
+  {:level :warning :warn-only-on-interop true}}
+
+ :skip-comments true}
diff --git a/modules/cache-collector/Makefile b/modules/cache-collector/Makefile
new file mode 100644
index 000000000..7510b665c
--- /dev/null
+++ b/modules/cache-collector/Makefile
@@ -0,0 +1,22 @@
+lint:
+	clj-kondo --lint src test deps.edn
+
+prep:
+	clojure -X:deps prep
+
+test: prep
+	clojure -M:test:kaocha --profile :ci
+
+test-coverage: prep
+	clojure -M:test:coverage
+
+deps-tree:
+	clojure -X:deps tree
+
+deps-list:
+	clojure -X:deps list
+
+clean:
+	rm -rf .clj-kondo/.cache .cpcache target
+
+.PHONY: lint prep test test-coverage deps-tree deps-list clean
diff --git a/modules/cache-collector/deps.edn b/modules/cache-collector/deps.edn
new file mode 100644
index 000000000..cdb76985b
--- /dev/null
+++ b/modules/cache-collector/deps.edn
@@ -0,0 +1,45 @@
+{:deps
+ {blaze/metrics
+  {:local/root "../metrics"}
+
+  blaze/module-base
+  {:local/root "../module-base"}
+
+  com.github.ben-manes.caffeine/caffeine
+  {:mvn/version "3.1.8"}}
+
+ :aliases
+ {:test
+  {:extra-paths ["test"]
+
+   :extra-deps
+   {blaze/module-test-util
+    {:local/root "../module-test-util"}}}
+
+  :kaocha
+  {:extra-deps
+   {lambdaisland/kaocha
+    {:mvn/version "1.85.1342"}}
+
+   :main-opts ["-m" "kaocha.runner"]}
+
+  :test-perf
+  {:extra-paths ["test-perf"]
+
+   :extra-deps
+   {blaze/fhir-test-util
+    {:local/root "../fhir-test-util"}
+
+    criterium/criterium
+    {:mvn/version "0.4.6"}
+
+    org.openjdk.jol/jol-core
+    {:mvn/version "0.17"}}}
+
+  :coverage
+  {:extra-deps
+   {cloverage/cloverage
+    {:mvn/version "1.2.4"}}
+
+   :main-opts ["-m" "cloverage.coverage" "--codecov" "-p" "src" "-s" "test"
+               "-e" ".+spec"]}}}
diff --git a/modules/db/src/blaze/db/cache_collector.clj b/modules/cache-collector/src/blaze/cache_collector.clj
similarity index 75%
rename from modules/db/src/blaze/db/cache_collector.clj
rename to modules/cache-collector/src/blaze/cache_collector.clj
index 599684c94..62b6bcb6f 100644
--- a/modules/db/src/blaze/db/cache_collector.clj
+++ b/modules/cache-collector/src/blaze/cache_collector.clj
@@ -1,12 +1,12 @@
-(ns blaze.db.cache-collector
+(ns blaze.cache-collector
   (:require
-    [blaze.db.cache-collector.protocols :as p]
-    [blaze.db.cache-collector.spec]
+    [blaze.cache-collector.protocols :as p]
+    [blaze.cache-collector.spec]
     [blaze.metrics.core :as metrics]
     [clojure.spec.alpha :as s]
     [integrant.core :as ig])
   (:import
-    [com.github.benmanes.caffeine.cache Cache]
+    [com.github.benmanes.caffeine.cache Cache AsyncCache]
     [com.github.benmanes.caffeine.cache.stats CacheStats]))
 
 
@@ -18,7 +18,12 @@
   (-stats [cache]
     (.stats cache))
   (-estimated-size [cache]
-    (.estimatedSize cache)))
+    (.estimatedSize cache))
+  AsyncCache
+  (-stats [cache]
+    (.stats (.synchronous cache)))
+  (-estimated-size [cache]
+    (.estimatedSize (.synchronous cache))))
 
 
 (defn- sample-xf [f]
@@ -42,49 +47,49 @@
         [name (p/-stats cache) (p/-estimated-size cache)]))))
 
 
-(defmethod ig/pre-init-spec :blaze.db/cache-collector [_]
+(defmethod ig/pre-init-spec :blaze/cache-collector [_]
   (s/keys :req-un [::caches]))
 
 
-(defmethod ig/init-key :blaze.db/cache-collector
+(defmethod ig/init-key :blaze/cache-collector
   [_ {:keys [caches]}]
   (metrics/collector
     (let [stats (into [] mapper caches)]
       [(counter-metric
-         "blaze_db_cache_hits_total"
+         "blaze_cache_hits_total"
          "Returns the number of times Cache lookup methods have returned a cached value."
          (fn [stats _] (.hitCount ^CacheStats stats))
          stats)
        (counter-metric
-         "blaze_db_cache_misses_total"
+         "blaze_cache_misses_total"
          "Returns the number of times Cache lookup methods have returned an uncached (newly loaded) value, or null."
          (fn [stats _] (.missCount ^CacheStats stats))
          stats)
        (counter-metric
-         "blaze_db_cache_load_successes_total"
+         "blaze_cache_load_successes_total"
          "Returns the number of times Cache lookup methods have successfully loaded a new value."
          (fn [stats _] (.loadSuccessCount ^CacheStats stats))
          stats)
        (counter-metric
-         "blaze_db_cache_load_failures_total"
+         "blaze_cache_load_failures_total"
          "Returns the number of times Cache lookup methods failed to load a new value, either because no value was found or an exception was thrown while loading."
          (fn [stats _] (.loadFailureCount ^CacheStats stats))
          stats)
        (counter-metric
-         "blaze_db_cache_load_seconds_total"
+         "blaze_cache_load_seconds_total"
          "Returns the total number of seconds the cache has spent loading new values."
          (fn [stats _] (/ (double (.totalLoadTime ^CacheStats stats)) 1e9))
          stats)
        (counter-metric
-         "blaze_db_cache_evictions_total"
+         "blaze_cache_evictions_total"
          "Returns the number of times an entry has been evicted."
          (fn [stats _] (.evictionCount ^CacheStats stats))
          stats)
        (gauge-metric
-         "blaze_db_cache_estimated_size"
+         "blaze_cache_estimated_size"
          "Returns the approximate number of entries in this cache."
          (fn [_ estimated-size] estimated-size)
          stats)])))
 
 
-(derive :blaze.db/cache-collector :blaze.metrics/collector)
+(derive :blaze/cache-collector :blaze.metrics/collector)
diff --git a/modules/db/src/blaze/db/cache_collector/protocols.clj b/modules/cache-collector/src/blaze/cache_collector/protocols.clj
similarity index 62%
rename from modules/db/src/blaze/db/cache_collector/protocols.clj
rename to modules/cache-collector/src/blaze/cache_collector/protocols.clj
index b8224f17f..6b211f0ae 100644
--- a/modules/db/src/blaze/db/cache_collector/protocols.clj
+++ b/modules/cache-collector/src/blaze/cache_collector/protocols.clj
@@ -1,4 +1,4 @@
-(ns blaze.db.cache-collector.protocols)
+(ns blaze.cache-collector.protocols)
 
 
 (defprotocol StatsCache
diff --git a/modules/cache-collector/src/blaze/cache_collector/spec.clj b/modules/cache-collector/src/blaze/cache_collector/spec.clj
new file mode 100644
index 000000000..7e4378a17
--- /dev/null
+++ b/modules/cache-collector/src/blaze/cache_collector/spec.clj
@@ -0,0 +1,8 @@
+(ns blaze.cache-collector.spec
+  (:require
+    [blaze.cache-collector.protocols :as p]
+    [clojure.spec.alpha :as s]))
+
+
+(s/def :blaze.cache-collector/caches
+  (s/map-of string? (s/nilable #(satisfies? p/StatsCache %))))
diff --git a/modules/db/test/blaze/db/cache_collector_test.clj b/modules/cache-collector/test/blaze/cache_collector_test.clj
similarity index 63%
rename from modules/db/test/blaze/db/cache_collector_test.clj
rename to modules/cache-collector/test/blaze/cache_collector_test.clj
index 8b0f7d826..7ea7be27b 100644
--- a/modules/db/test/blaze/db/cache_collector_test.clj
+++ b/modules/cache-collector/test/blaze/cache_collector_test.clj
@@ -1,6 +1,6 @@
-(ns blaze.db.cache-collector-test
+(ns blaze.cache-collector-test
   (:require
-    [blaze.db.cache-collector]
+    [blaze.cache-collector]
     [blaze.metrics.core :as metrics]
     [blaze.module.test-util :refer [with-system]]
     [blaze.test-util :as tu :refer [given-thrown]]
@@ -25,55 +25,55 @@
 
 
 (def config
-  {:blaze.db/cache-collector
+  {:blaze/cache-collector
    {:caches {"name-135224" cache "name-093214" nil}}})
 
 
 (deftest init-test
   (testing "nil config"
-    (given-thrown (ig/init {:blaze.db/cache-collector nil})
-      :key := :blaze.db/cache-collector
+    (given-thrown (ig/init {:blaze/cache-collector nil})
+      :key := :blaze/cache-collector
       :reason := ::ig/build-failed-spec
       [:explain ::s/problems 0 :pred] := `map?))
 
   (testing "missing config"
-    (given-thrown (ig/init {:blaze.db/cache-collector {}})
-      :key := :blaze.db/cache-collector
+    (given-thrown (ig/init {:blaze/cache-collector {}})
+      :key := :blaze/cache-collector
       :reason := ::ig/build-failed-spec
       [:explain ::s/problems 0 :pred] := `(fn ~'[%] (contains? ~'% :caches))))
 
   (testing "invalid caches"
-    (given-thrown (ig/init {:blaze.db/cache-collector {:caches ::invalid}})
-      :key := :blaze.db/cache-collector
+    (given-thrown (ig/init {:blaze/cache-collector {:caches ::invalid}})
+      :key := :blaze/cache-collector
       :reason := ::ig/build-failed-spec
       [:explain ::s/problems 0 :pred] := `map?
       [:explain ::s/problems 0 :val] := ::invalid)))
 
 
 (deftest cache-collector-test
-  (with-system [{collector :blaze.db/cache-collector} config]
+  (with-system [{collector :blaze/cache-collector} config]
 
     (testing "all zero on fresh cache"
       (given (metrics/collect collector)
-        [0 :name] := "blaze_db_cache_hits"
+        [0 :name] := "blaze_cache_hits"
         [0 :type] := :counter
         [0 :samples 0 :value] := 0.0
-        [1 :name] := "blaze_db_cache_misses"
+        [1 :name] := "blaze_cache_misses"
         [1 :type] := :counter
         [1 :samples 0 :value] := 0.0
-        [2 :name] := "blaze_db_cache_load_successes"
+        [2 :name] := "blaze_cache_load_successes"
         [2 :type] := :counter
         [2 :samples 0 :value] := 0.0
-        [3 :name] := "blaze_db_cache_load_failures"
+        [3 :name] := "blaze_cache_load_failures"
         [3 :type] := :counter
         [3 :samples 0 :value] := 0.0
-        [4 :name] := "blaze_db_cache_load_seconds"
+        [4 :name] := "blaze_cache_load_seconds"
         [4 :type] := :counter
         [4 :samples 0 :value] := 0.0
-        [5 :name] := "blaze_db_cache_evictions"
+        [5 :name] := "blaze_cache_evictions"
         [5 :type] := :counter
         [5 :samples 0 :value] := 0.0
-        [6 :name] := "blaze_db_cache_estimated_size"
+        [6 :name] := "blaze_cache_estimated_size"
         [6 :type] := :gauge
         [6 :samples 0 :value] := 0.0))
 
@@ -82,17 +82,17 @@
       (Thread/sleep 100)
 
       (given (metrics/collect collector)
-        [0 :name] := "blaze_db_cache_hits"
+        [0 :name] := "blaze_cache_hits"
         [0 :samples 0 :value] := 0.0
-        [1 :name] := "blaze_db_cache_misses"
+        [1 :name] := "blaze_cache_misses"
         [1 :samples 0 :value] := 1.0
-        [2 :name] := "blaze_db_cache_load_successes"
+        [2 :name] := "blaze_cache_load_successes"
         [2 :samples 0 :value] := 1.0
-        [3 :name] := "blaze_db_cache_load_failures"
+        [3 :name] := "blaze_cache_load_failures"
         [3 :samples 0 :value] := 0.0
-        [5 :name] := "blaze_db_cache_evictions"
+        [5 :name] := "blaze_cache_evictions"
         [5 :samples 0 :value] := 0.0
-        [6 :name] := "blaze_db_cache_estimated_size"
+        [6 :name] := "blaze_cache_estimated_size"
         [6 :samples 0 :value] := 1.0))
 
     (testing "one loads and one hit"
@@ -100,15 +100,15 @@
       (Thread/sleep 100)
 
       (given (metrics/collect collector)
-        [0 :name] := "blaze_db_cache_hits"
+        [0 :name] := "blaze_cache_hits"
         [0 :samples 0 :value] := 1.0
-        [1 :name] := "blaze_db_cache_misses"
+        [1 :name] := "blaze_cache_misses"
         [1 :samples 0 :value] := 1.0
-        [2 :name] := "blaze_db_cache_load_successes"
+        [2 :name] := "blaze_cache_load_successes"
         [2 :samples 0 :value] := 1.0
-        [3 :name] := "blaze_db_cache_load_failures"
+        [3 :name] := "blaze_cache_load_failures"
         [3 :samples 0 :value] := 0.0
-        [5 :name] := "blaze_db_cache_evictions"
+        [5 :name] := "blaze_cache_evictions"
         [5 :samples 0 :value] := 0.0
-        [6 :name] := "blaze_db_cache_estimated_size"
+        [6 :name] := "blaze_cache_estimated_size"
         [6 :samples 0 :value] := 1.0))))
diff --git a/modules/cache-collector/tests.edn b/modules/cache-collector/tests.edn
new file mode 100644
index 000000000..94fe5636c
--- /dev/null
+++ b/modules/cache-collector/tests.edn
@@ -0,0 +1,5 @@
+#kaocha/v1
+    #merge
+        [{}
+         #profile {:ci {:reporter kaocha.report/documentation
+                        :color? false}}]
diff --git a/modules/cql/.clj-kondo/config.edn b/modules/cql/.clj-kondo/config.edn
index 7172e6ab1..378f20272 100644
--- a/modules/cql/.clj-kondo/config.edn
+++ b/modules/cql/.clj-kondo/config.edn
@@ -9,7 +9,9 @@
   blaze.elm.compiler.macros/defnaryop clojure.core/defn
   blaze.elm.compiler.macros/defaggop clojure.core/defn
   blaze.elm.compiler.macros/defbinopp clojure.core/defn
-  blaze.elm.compiler.macros/defunopp clojure.core/defn}
+  blaze.elm.compiler.macros/defunopp clojure.core/defn
+  prometheus.alpha/defcounter clojure.core/def
+  prometheus.alpha/defhistogram clojure.core/def}
 
  :linters
  {;; because of macros in modules/cql/src/blaze/elm/compiler.clj
@@ -43,6 +45,7 @@
     blaze.cql-translator t
     blaze.db.api d
     blaze.elm.compiler c
+    blaze.elm.compiler.expr-cache ec
     blaze.elm.compiler.external-data ed
     blaze.elm.expression expr
     cognitect.anomalies anom
diff --git a/modules/cql/src/blaze/elm/code.clj b/modules/cql/src/blaze/elm/code.clj
index bce654696..8347c26cc 100644
--- a/modules/cql/src/blaze/elm/code.clj
+++ b/modules/cql/src/blaze/elm/code.clj
@@ -27,6 +27,8 @@
   core/Expression
   (-static [_]
     true)
+  (-attach-cache [expr _]
+    expr)
   (-eval [this _ _ _]
     this)
   (-form [_]
diff --git a/modules/cql/src/blaze/elm/compiler.clj b/modules/cql/src/blaze/elm/compiler.clj
index 5f3679dce..093ec8c3f 100644
--- a/modules/cql/src/blaze/elm/compiler.clj
+++ b/modules/cql/src/blaze/elm/compiler.clj
@@ -44,5 +44,9 @@
   (core/compile* context expression))
 
 
+(defn attach-cache [context expression]
+  (core/-attach-cache expression context))
+
+
 (defn form [expression]
   (core/-form expression))
diff --git a/modules/cql/src/blaze/elm/compiler/arithmetic_operators.clj b/modules/cql/src/blaze/elm/compiler/arithmetic_operators.clj
index 7fd8a573e..c9c7b4f34 100644
--- a/modules/cql/src/blaze/elm/compiler/arithmetic_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/arithmetic_operators.clj
@@ -138,22 +138,28 @@
 
 
 ;; 16.19. Round
+(defn round-op [operand precision]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (round-op (core/-attach-cache operand context)
+                (core/-attach-cache precision context)))
+    (-eval [_ context resource scope]
+      (p/round (core/-eval operand context resource scope)
+               (core/-eval precision context resource scope)))
+    (-form [_]
+      (->> (some-> (core/-form precision) list)
+           (cons (core/-form operand))
+           (cons 'round)))))
+
 (defmethod core/compile* :elm.compiler.type/round
   [context {:keys [operand precision]}]
   (let [operand (core/compile* context operand)
         precision (some->> precision (core/compile* context))]
     (if (and (core/static? operand) (core/static? precision))
       (p/round operand precision)
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (p/round (core/-eval operand context resource scope)
-                   (core/-eval precision context resource scope)))
-        (-form [_]
-          (->> (some-> (core/-form precision) list)
-               (cons (core/-form operand))
-               (cons 'round)))))))
+      (round-op operand precision))))
 
 
 ;; 16.20. Subtract
diff --git a/modules/cql/src/blaze/elm/compiler/clinical_operators.clj b/modules/cql/src/blaze/elm/compiler/clinical_operators.clj
index 49f5f031a..88509667f 100644
--- a/modules/cql/src/blaze/elm/compiler/clinical_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/clinical_operators.clj
@@ -22,6 +22,8 @@
         (reify core/Expression
           (-static [_]
             false)
+          (-attach-cache [expr _]
+            expr)
           (-eval [_ context resource scope]
             (p/duration-between
               (core/-eval birth-date context resource scope)
diff --git a/modules/cql/src/blaze/elm/compiler/comparison_operators.clj b/modules/cql/src/blaze/elm/compiler/comparison_operators.clj
index 2afa94c57..5a9e376fa 100644
--- a/modules/cql/src/blaze/elm/compiler/comparison_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/comparison_operators.clj
@@ -13,6 +13,11 @@
 (defbinop equal [operand-1 operand-2]
   (p/equal operand-1 operand-2))
 
+(comment
+  (macroexpand-1
+    '(defbinop equal [operand-1 operand-2]
+       (p/equal operand-1 operand-2))))
+
 
 ;; 12.2. Equivalent
 (defbinop equivalent [operand-1 operand-2]
diff --git a/modules/cql/src/blaze/elm/compiler/conditional_operators.clj b/modules/cql/src/blaze/elm/compiler/conditional_operators.clj
index 7b2ccc72b..6efbdb99f 100644
--- a/modules/cql/src/blaze/elm/compiler/conditional_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/conditional_operators.clj
@@ -9,6 +9,51 @@
 
 
 ;; 15.1. Case
+(defn- attach-cache [items context]
+  (map
+    (fn [[when then]]
+      [(core/-attach-cache when context)
+       (core/-attach-cache then context)])
+    items))
+
+(defn- comparand-case-op [comparand items else]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (comparand-case-op
+        (core/-attach-cache comparand context)
+        (attach-cache items context)
+        (core/-attach-cache else context)))
+    (-eval [_ context resource scope]
+      (let [comparand (core/-eval comparand context resource scope)]
+        (loop [[[when then] & next-items] items]
+          (if (p/equal comparand (core/-eval when context resource scope))
+            (core/-eval then context resource scope)
+            (if (empty? next-items)
+              (core/-eval else context resource scope)
+              (recur next-items))))))
+    (-form [_]
+      `(~'case ~(core/-form comparand) ~@(map core/-form (flatten items)) ~(core/-form else)))))
+
+(defn- multi-conditional-case-op [items else]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (multi-conditional-case-op
+        (attach-cache items context)
+        (core/-attach-cache else context)))
+    (-eval [_ context resource scope]
+      (loop [[[when then] & next-items] items]
+        (if (core/-eval when context resource scope)
+          (core/-eval then context resource scope)
+          (if (empty? next-items)
+            (core/-eval else context resource scope)
+            (recur next-items)))))
+    (-form [_]
+      `(~'case ~@(map core/-form (flatten items)) ~(core/-form else)))))
+
 (defmethod core/compile* :elm.compiler.type/case
   [context {:keys [comparand else] items :caseItem}]
   (let [comparand (some->> comparand (core/compile* context))
@@ -20,42 +65,28 @@
           items)
         else (core/compile* context else)]
     (if comparand
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (let [comparand (core/-eval comparand context resource scope)]
-            (loop [[[when then] & next-items] items]
-              (if (p/equal comparand (core/-eval when context resource scope))
-                (core/-eval then context resource scope)
-                (if (empty? next-items)
-                  (core/-eval else context resource scope)
-                  (recur next-items))))))
-        (-form [_]
-          `(~'case ~(core/-form comparand) ~@(map core/-form (flatten items)) ~else)))
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (loop [[[when then] & next-items] items]
-            (if (core/-eval when context resource scope)
-              (core/-eval then context resource scope)
-              (if (empty? next-items)
-                (core/-eval else context resource scope)
-                (recur next-items)))))
-        (-form [_]
-          `(~'case ~@(map core/-form (flatten items)) ~else))))))
+      (comparand-case-op comparand items else)
+      (multi-conditional-case-op items else))))
 
 
 ;; 15.2. If
-(defrecord IfExpression [condition then else]
-  core/Expression
-  (-static [_]
-    false)
-  (-eval [_ context resource scope]
-    (if (core/-eval condition context resource scope)
-      (core/-eval then context resource scope)
-      (core/-eval else context resource scope))))
+(defn- if-op [condition then else]
+  (reify
+    core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (if-op
+        (core/-attach-cache condition context)
+        (core/-attach-cache then context)
+        (core/-attach-cache else context)))
+    (-eval [_ context resource scope]
+      (if (core/-eval condition context resource scope)
+        (core/-eval then context resource scope)
+        (core/-eval else context resource scope)))
+    (-form [_]
+      (list 'if (core/-form condition) (core/-form then)
+            (core/-form else)))))
 
 
 (defmethod core/compile* :elm.compiler.type/if
@@ -64,5 +95,5 @@
     (cond
       (true? condition) (core/compile* context then)
       (or (false? condition) (nil? condition)) (core/compile* context else)
-      :else (->IfExpression condition (core/compile* context then)
-                            (core/compile* context else)))))
+      :else (if-op condition (core/compile* context then)
+                   (core/compile* context else)))))
diff --git a/modules/cql/src/blaze/elm/compiler/core.clj b/modules/cql/src/blaze/elm/compiler/core.clj
index 813200722..0d2b54219 100644
--- a/modules/cql/src/blaze/elm/compiler/core.clj
+++ b/modules/cql/src/blaze/elm/compiler/core.clj
@@ -5,6 +5,7 @@
     [clojure.string :as str]
     [cuerdas.core :as c-str])
   (:import
+    [clojure.lang PersistentVector]
     [java.time.temporal ChronoUnit]))
 
 
@@ -13,6 +14,7 @@
 
 (defprotocol Expression
   (-static [expression])
+  (-attach-cache [expression context])
   (-eval [expression context resource scope]
     "Evaluates `expression` on `resource` using `context` and optional `scope`
     for scoped expressions inside queries.")
@@ -23,10 +25,16 @@
   (satisfies? Expression x))
 
 
+(defn static? [x]
+  (-static x))
+
+
 (extend-protocol Expression
   nil
   (-static [_]
     true)
+  (-attach-cache [expr _]
+    expr)
   (-eval [expr _ _ _]
     expr)
   (-form [_]
@@ -35,14 +43,22 @@
   Object
   (-static [_]
     true)
+  (-attach-cache [expr _]
+    expr)
   (-eval [expr _ _ _]
     expr)
   (-form [expr]
-    expr))
-
+    expr)
 
-(defn static? [x]
-  (-static x))
+  PersistentVector
+  (-static [_]
+    true)
+  (-attach-cache [expr _]
+    expr)
+  (-eval [expr _ _ _]
+    expr)
+  (-form [expr]
+    (mapv -form expr)))
 
 
 (defmulti compile*
diff --git a/modules/cql/src/blaze/elm/compiler/date_time_operators.clj b/modules/cql/src/blaze/elm/compiler/date_time_operators.clj
index be0c08f03..b81677d9f 100644
--- a/modules/cql/src/blaze/elm/compiler/date_time_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/date_time_operators.clj
@@ -29,6 +29,61 @@
 
 
 ;; 18.6. Date
+(defn date-op [year month day]
+  (reify
+    system/SystemType
+    (-type [_] :system/date)
+    core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (date-op
+        (core/-attach-cache year context)
+        (core/-attach-cache month context)
+        (core/-attach-cache day context)))
+    (-eval [_ context resource scope]
+      (when-let [year (core/-eval year context resource scope)]
+        (if-let [month (core/-eval month context resource scope)]
+          (if-let [day (core/-eval day context resource scope)]
+            (system/date year month day)
+            (system/date year month))
+          (system/date year))))
+    (-form [_]
+      (list 'date (core/-form year) (core/-form month) (core/-form day)))))
+
+(defn year-month-op [year month]
+  (reify
+    system/SystemType
+    (-type [_] :system/date)
+    core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (year-month-op
+        (core/-attach-cache year context)
+        (core/-attach-cache month context)))
+    (-eval [_ context resource scope]
+      (when-let [year (core/-eval year context resource scope)]
+        (if-let [month (core/-eval month context resource scope)]
+          (system/date year month)
+          (system/date year))))
+    (-form [_]
+      (list 'date (core/-form year) (core/-form month)))))
+
+(defn year-op [year]
+  (reify
+    system/SystemType
+    (-type [_] :system/date)
+    core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (year-op (core/-attach-cache year context)))
+    (-eval [_ context resource scope]
+      (some-> (core/-eval year context resource scope) system/date))
+    (-form [_]
+      (list 'date (core/-form year)))))
+
 (defmethod core/compile* :elm.compiler.type/date
   [context {:keys [year month day]}]
   (let [year (some->> year (core/compile* context))
@@ -39,55 +94,19 @@
       (system/date year month day)
 
       (some? day)
-      (reify
-        system/SystemType
-        (-type [_] :system/date)
-        core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (when-let [year (core/-eval year context resource scope)]
-            (if-let [month (core/-eval month context resource scope)]
-              (if-let [day (core/-eval day context resource scope)]
-                (system/date year month day)
-                (system/date year month))
-              (system/date year))))
-        (-form [_]
-          (list 'date (core/-form year) (core/-form month) (core/-form day))))
+      (date-op year month day)
 
       (and (int? month) (int? year))
       (system/date year month)
 
       (some? month)
-      (reify
-        system/SystemType
-        (-type [_] :system/date)
-        core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (when-let [year (core/-eval year context resource scope)]
-            (if-let [month (core/-eval month context resource scope)]
-              (system/date year month)
-              (system/date year))))
-        (-form [_]
-          (list 'date (core/-form year) (core/-form month))))
+      (year-month-op year month)
 
       (int? year)
       (system/date year)
 
       :else
-      (when year
-        (reify
-          system/SystemType
-          (-type [_] :system/date)
-          core/Expression
-          (-static [_]
-            false)
-          (-eval [_ context resource scope]
-            (some-> (core/-eval year context resource scope) system/date))
-          (-form [_]
-            (list 'date (core/-form year))))))))
+      (some-> year year-op))))
 
 
 ;; 18.7. DateFrom
diff --git a/modules/cql/src/blaze/elm/compiler/expr_cache.clj b/modules/cql/src/blaze/elm/compiler/expr_cache.clj
new file mode 100644
index 000000000..5e75cb34f
--- /dev/null
+++ b/modules/cql/src/blaze/elm/compiler/expr_cache.clj
@@ -0,0 +1,61 @@
+(ns blaze.elm.compiler.expr-cache
+  (:require
+    [blaze.elm.compiler.external-data]
+    [prometheus.alpha :as prom :refer [defhistogram]])
+  (:import
+    [blaze.elm.compiler.external_data Resource]
+    [com.google.common.hash BloomFilter Funnel Funnels]
+    [java.nio.charset StandardCharsets]))
+
+
+(set! *warn-on-reflection* true)
+
+
+(defhistogram bloom-filter-bytes
+  "Bloom filter sizes in bytes."
+  {:namespace "blaze"
+   :subsystem "cql_expr_cache"}
+  (take 12 (iterate #(* 4 %) 1)))
+
+
+(defprotocol Cache
+  (-might-contain [_ resource])
+  (-mem-size [_]))
+
+
+(defn cache? [x]
+  (satisfies? Cache x))
+
+
+(defn might-contain? [cache resource]
+  (-might-contain cache resource))
+
+
+(defn mem-size
+  "Returns the size of the cache in memory in bytes."
+  [cache]
+  (-mem-size cache))
+
+
+(def ^:private ^Funnel id-funnel
+  (Funnels/stringFunnel StandardCharsets/ISO_8859_1))
+
+
+(defn- calc-mem-size [n p]
+  (long (/ (* (- n) (Math/log p)) (* (Math/log 2) (Math/log 2)) 8)))
+
+
+(defn cache [t resource-ids]
+  (let [n (count resource-ids)
+        p (double 0.01)
+        filter (BloomFilter/create id-funnel n p)
+        mem-size (calc-mem-size n p)]
+    (prom/observe! bloom-filter-bytes mem-size)
+    (run! #(.put filter %) resource-ids)
+    (reify
+      Cache
+      (-might-contain [_ resource]
+        (or (< t (.lastChangeT ^Resource resource))
+            (.mightContain filter (.id ^Resource resource))))
+      (-mem-size [_]
+        mem-size))))
diff --git a/modules/cql/src/blaze/elm/compiler/external_data.clj b/modules/cql/src/blaze/elm/compiler/external_data.clj
index 2daf1fd0f..fbf85252f 100644
--- a/modules/cql/src/blaze/elm/compiler/external_data.clj
+++ b/modules/cql/src/blaze/elm/compiler/external_data.clj
@@ -23,9 +23,18 @@
 (set! *warn-on-reflection* true)
 
 
+(definterface Resource
+  (^String id [])
+  (^long lastChangeT []))
+
+
 ;; A resource that is a wrapper of a resource-handle that will lazily pull the
 ;; resource content if some property other than :id is accessed.
-(deftype Resource [db handle content]
+(deftype ResourceImpl [db ^String id handle ^long last-change-t content]
+  Resource
+  (id [_] id)
+  (lastChangeT [_] last-change-t)
+
   p/FhirType
   (-type [_]
     (p/-type handle))
@@ -35,7 +44,7 @@
     (.valAt r key nil))
   (valAt [_ key not-found]
     (case key
-      :id (rh/id handle)
+      :id id
       (-> (or @content (vreset! content @(d/pull-content db handle)))
           (get key not-found))))
 
@@ -48,8 +57,21 @@
   (instance? Resource x))
 
 
+(defn- patient-last-change-t [db handle]
+  (max (or (d/patient-compartment-last-change-t db (rh/id handle)) (d/t db))
+       (rh/t handle)))
+
+
+(defn- last-change-t [db handle]
+  (case (p/-type handle)
+    :fhir/Patient
+    (patient-last-change-t db handle)
+    (d/t db)))
+
+
 (defn mk-resource [db handle]
-  (Resource. db handle (volatile! nil)))
+  (ResourceImpl. db (rh/id handle) handle (last-change-t db handle)
+                 (volatile! nil)))
 
 
 (defn resource-mapper [db]
@@ -91,6 +113,8 @@
     (reify core/Expression
       (-static [_]
         false)
+      (-attach-cache [expr _]
+        expr)
       (-eval [_ {:keys [db]} {:keys [id]} _]
         (coll/eduction (resource-mapper db) (d/execute-query db query id)))
       (-form [_]
@@ -107,6 +131,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [expr _]
+    expr)
   (-eval [_ {:keys [db]} resource _]
     (let [{{:keys [reference]} :subject} resource]
       (when reference
@@ -135,6 +161,8 @@
     (reify core/Expression
       (-static [_]
         false)
+      (-attach-cache [expr _]
+        expr)
       (-eval [_ {:keys [db]} {:keys [id]} _]
         (coll/eduction
           (resource-mapper db)
@@ -147,6 +175,8 @@
   (reify core/Expression
     (-static [_]
       false)
+    (-attach-cache [expr _]
+      expr)
     (-eval [_ _ resource _]
       [resource])
     (-form [_]
@@ -165,6 +195,8 @@
   (reify core/Expression
     (-static [_]
       false)
+    (-attach-cache [expr _]
+      expr)
     (-eval [_ context resource scope]
       (when-let [context-resource (core/-eval related-context-expr context resource scope)]
         (core/-eval
@@ -187,6 +219,8 @@
               (reify core/Expression
                 (-static [_]
                   false)
+                (-attach-cache [expr _]
+                  expr)
                 (-eval [_ {:keys [db] :as context} resource scope]
                   (when-let [{:keys [id]} (core/-eval context-expr context resource scope)]
                     (when (string? id)
@@ -206,6 +240,8 @@
     (reify core/Expression
       (-static [_]
         false)
+      (-attach-cache [expr _]
+        expr)
       (-eval [_ {:keys [db]} _ _]
         (coll/eduction (resource-mapper db) (d/type-list db data-type)))
       (-form [_]
@@ -215,6 +251,8 @@
         (reify core/Expression
           (-static [_]
             false)
+          (-attach-cache [expr _]
+            expr)
           (-eval [_ {:keys [db]} _ _]
             (coll/eduction (resource-mapper db) (d/execute-query db query)))
           (-form [_]
diff --git a/modules/cql/src/blaze/elm/compiler/function.clj b/modules/cql/src/blaze/elm/compiler/function.clj
index e9cefd97c..c8996f1cc 100644
--- a/modules/cql/src/blaze/elm/compiler/function.clj
+++ b/modules/cql/src/blaze/elm/compiler/function.clj
@@ -7,6 +7,9 @@
   (reify core/Expression
     (-static [_]
       false)
+    (-attach-cache [_ context]
+      (arity-n name (core/-attach-cache fn-expr context) operand-names
+               (map #(core/-attach-cache % context) operands)))
     (-eval [_ context resource scope]
       (let [values (map #(core/-eval % context resource scope) operands)]
         (core/-eval fn-expr context resource (merge scope (zipmap operand-names values)))))
diff --git a/modules/cql/src/blaze/elm/compiler/interval_operators.clj b/modules/cql/src/blaze/elm/compiler/interval_operators.clj
index 2aa313a7f..cf7e046a5 100644
--- a/modules/cql/src/blaze/elm/compiler/interval_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/interval_operators.clj
@@ -24,6 +24,15 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [_ context]
+    (->IntervalExpression
+      type
+      (core/-attach-cache low context)
+      (core/-attach-cache high context)
+      (core/-attach-cache low-closed-expression context)
+      (core/-attach-cache high-closed-expression context)
+      low-closed
+      high-closed))
   (-eval [_ context resource scope]
     (let [low (core/-eval low context resource scope)
           high (core/-eval high context resource scope)
@@ -87,6 +96,11 @@
   (p/after operand-1 operand-2 precision))
 
 
+(comment
+  (macroexpand-1
+    '(defbinopp after [operand-1 operand-2 precision]
+       (p/after operand-1 operand-2 precision))))
+
 ;; 19.3. Before
 (defbinopp before [operand-1 operand-2 precision]
   (p/before operand-1 operand-2 precision))
@@ -197,6 +211,15 @@
       (throw (ex-info (core/append-locator "Invalid non-unit interval in `PointFrom` expression at" locator)
                       {:expression expression})))))
 
+(comment
+  (macroexpand-1
+    '(defunop point-from [interval {{:keys [locator]} :operand :as expression}]
+       (when interval
+         (if (p/equal (:start interval) (:end interval))
+           (:start interval)
+           (throw (ex-info (core/append-locator "Invalid non-unit interval in `PointFrom` expression at" locator)
+                           {:expression expression})))))))
+
 
 ;; 19.24. ProperContains
 (defbinopp proper-contains [list-or-interval x precision]
@@ -225,6 +248,12 @@
   start)
 
 
+(comment
+  (macroexpand-1
+    '(defunop start [{:keys [start]}]
+       start))
+  )
+
 ;; 19.30. Starts
 (defbinopp starts [x y _]
   (and (p/equal (:start x) (:start y))
diff --git a/modules/cql/src/blaze/elm/compiler/library.clj b/modules/cql/src/blaze/elm/compiler/library.clj
index 966e98024..c1aa9dec1 100644
--- a/modules/cql/src/blaze/elm/compiler/library.clj
+++ b/modules/cql/src/blaze/elm/compiler/library.clj
@@ -60,11 +60,12 @@
   itself is returned.
 
   Returns an anomaly on errors."
-  {:arglists '([context expression-def])}
+  {:arglists '([context parameter-def])}
   [context {:keys [default] :as parameter-def}]
   (if (some? default)
     (-> (ba/try-anomaly
-          (assoc parameter-def :default (c/compile context default)))
+          (let [context (assoc context :eval-context "Unfiltered")]
+            (assoc parameter-def :default (c/compile context default))))
         (ba/exceptionally
           #(assoc % :context context :elm/expression default)))
     parameter-def))
diff --git a/modules/cql/src/blaze/elm/compiler/library_spec.clj b/modules/cql/src/blaze/elm/compiler/library_spec.clj
index 5ad47d211..1508e9aa1 100644
--- a/modules/cql/src/blaze/elm/compiler/library_spec.clj
+++ b/modules/cql/src/blaze/elm/compiler/library_spec.clj
@@ -36,6 +36,10 @@
   (s/keys :req-un [::c/expression-defs ::c/parameter-default-values]))
 
 
+(s/def ::c/options
+  map?)
+
+
 (s/fdef library/compile-library
-  :args (s/cat :node :blaze.db/node :library :elm/library :opts map?)
+  :args (s/cat :node :blaze.db/node :library :elm/library :opts ::c/options)
   :ret (s/or :library ::c/library :anomaly ::anom/anomaly))
diff --git a/modules/cql/src/blaze/elm/compiler/list_operators.clj b/modules/cql/src/blaze/elm/compiler/list_operators.clj
index 2f0c00c74..a0476670c 100644
--- a/modules/cql/src/blaze/elm/compiler/list_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/list_operators.clj
@@ -19,18 +19,21 @@
 
 
 ;; 20.1. List
+(defn list-op [elements]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (list-op (mapv #(core/-attach-cache % context) elements)))
+    (-eval [_ context resource scope]
+      (mapv #(core/-eval % context resource scope) elements))
+    (-form [_]
+      `(~'list ~@(map core/-form elements)))))
+
 (defmethod core/compile* :elm.compiler.type/list
   [context {elements :element}]
   (let [elements (mapv #(core/compile* context %) elements)]
-    (if (every? core/static? elements)
-      elements
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (mapv #(core/-eval % context resource scope) elements))
-        (-form [_]
-          `(~'list ~@(map core/-form elements)))))))
+    (cond-> elements (some (comp not core/static?) elements) list-op)))
 
 
 ;; 20.3. Current
@@ -40,6 +43,8 @@
     (reify core/Expression
       (-static [_]
         false)
+      (-attach-cache [expr _]
+        expr)
       (-eval [_ _ _ scopes]
         (get scopes scope))
       (-form [_]
@@ -47,6 +52,8 @@
     (reify core/Expression
       (-static [_]
         false)
+      (-attach-cache [expr _]
+        expr)
       (-eval [_ _ _ scope]
         scope)
       (-form [_]
@@ -66,14 +73,36 @@
       []
       list)))
 
+(comment
+  (macroexpand-1
+    '(defunop distinct [list]
+       (when list
+         (reduce
+           (fn [result x]
+             (if (p/contains result x nil)
+               result
+               (conj result x)))
+           []
+           list)))))
+
 
 ;; 20.8. Exists
 (defunop exists
-  {:optimizations #{:first :non-distinct}}
+  {:optimizations #{:first :non-distinct}
+   :cache true}
   [list]
   (not (coll/empty? list)))
 
 
+(comment
+  (macroexpand-1
+    '(defunop exists
+       {:optimizations #{:first :non-distinct}
+        :cache true}
+       [list]
+       (not (coll/empty? list)))))
+
+
 ;; 20.9. Filter
 (defmethod core/compile* :elm.compiler.type/filter
   [context {:keys [source condition scope]}]
@@ -104,18 +133,23 @@
 ;; 20.10. First
 ;;
 ;; TODO: orderBy
+(defn first-op [source]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (first-op (core/-attach-cache source context)))
+    (-eval [_ context resource scopes]
+      (coll/first (core/-eval source context resource scopes)))
+    (-form [_]
+      (list 'first (core/-form source)))))
+
 (defmethod core/compile* :elm.compiler.type/first
   [context {:keys [source]}]
   (let [source (core/compile* (assoc context :optimizations #{:first :non-distinct}) source)]
     (if (core/static? source)
       (first source)
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scopes]
-          (coll/first (core/-eval source context resource scopes)))
-        (-form [_]
-          (list 'first (core/-form source)))))))
+      (first-op source))))
 
 
 ;; 20.11. Flatten
diff --git a/modules/cql/src/blaze/elm/compiler/logical_operators.clj b/modules/cql/src/blaze/elm/compiler/logical_operators.clj
index 1d0829ba4..39afc0a62 100644
--- a/modules/cql/src/blaze/elm/compiler/logical_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/logical_operators.clj
@@ -9,10 +9,12 @@
 
 
 ;; 13.1. And
-(defn- nil-and-expr [x]
+(defn- and-nil-op [x]
   (reify core/Expression
     (-static [_]
       false)
+    (-attach-cache [_ context]
+      (and-nil-op (core/-attach-cache x context)))
     (-eval [_ context resource scope]
       (when (false? (core/-eval x context resource scope))
         false))
@@ -27,7 +29,25 @@
     true nil
     false false
     nil nil
-    (nil-and-expr x)))
+    (and-nil-op x)))
+
+
+(defn and-op [a b]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (and-op (core/-attach-cache a context) (core/-attach-cache b context)))
+    (-eval [_ context resource scope]
+      (let [a (core/-eval a context resource scope)]
+        (if (false? a)
+          false
+          (let [b (core/-eval b context resource scope)]
+            (cond
+              (false? b) false
+              (and (true? a) (true? b)) true)))))
+    (-form [_]
+      (list 'and (core/-form a) (core/-form b)))))
 
 
 (defn- dynamic-and
@@ -37,20 +57,8 @@
   (condp identical? b
     true a
     false false
-    nil (nil-and-expr a)
-    (reify core/Expression
-      (-static [_]
-        false)
-      (-eval [_ context resource scope]
-        (let [a (core/-eval a context resource scope)]
-          (if (false? a)
-            false
-            (let [b (core/-eval b context resource scope)]
-              (cond
-                (false? b) false
-                (and (true? a) (true? b)) true)))))
-      (-form [_]
-        (list 'and (core/-form a) (core/-form b))))))
+    nil (and-nil-op a)
+    (and-op a b)))
 
 
 (defmethod core/compile* :elm.compiler.type/and
@@ -70,16 +78,20 @@
 
 
 ;; 13.3 Not
+(declare not-op)
+
 (defunop not [operand]
   (when (some? operand)
     (not operand)))
 
 
 ;; 13.4. Or
-(defn- nil-or-expr [x]
+(defn- or-nil-op [x]
   (reify core/Expression
     (-static [_]
       false)
+    (-attach-cache [_ context]
+      (or-nil-op (core/-attach-cache x context)))
     (-eval [_ context resource scope]
       (when (true? (core/-eval x context resource scope))
         true))
@@ -94,7 +106,25 @@
     true true
     false nil
     nil nil
-    (nil-or-expr x)))
+    (or-nil-op x)))
+
+
+(defn or-op [a b]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (or-op (core/-attach-cache a context) (core/-attach-cache b context)))
+    (-eval [_ context resource scope]
+      (let [a (core/-eval a context resource scope)]
+        (if (true? a)
+          true
+          (let [b (core/-eval b context resource scope)]
+            (cond
+              (true? b) true
+              (and (false? a) (false? b)) false)))))
+    (-form [_]
+      (list 'or (core/-form a) (core/-form b)))))
 
 
 (defn- dynamic-or
@@ -104,20 +134,8 @@
   (condp identical? b
     true true
     false a
-    nil (nil-or-expr a)
-    (reify core/Expression
-      (-static [_]
-        false)
-      (-eval [_ context resource scope]
-        (let [a (core/-eval a context resource scope)]
-          (if (true? a)
-            true
-            (let [b (core/-eval b context resource scope)]
-              (cond
-                (true? b) true
-                (and (false? a) (false? b)) false)))))
-      (-form [_]
-        (list 'or (core/-form a) (core/-form b))))))
+    nil (or-nil-op a)
+    (or-op a b)))
 
 
 (defmethod core/compile* :elm.compiler.type/or
@@ -137,15 +155,7 @@
   [a b]
   (condp identical? b
     true
-    (reify core/Expression
-      (-static [_]
-        false)
-      (-eval [_ context resource scope]
-        (let [a (core/-eval a context resource scope)]
-          (when (some? a)
-            (not a))))
-      (-form [_]
-        (list 'not (core/-form a))))
+    (not-op a)
     false a
     nil nil
     (reify core/Expression
diff --git a/modules/cql/src/blaze/elm/compiler/macros.clj b/modules/cql/src/blaze/elm/compiler/macros.clj
index 617bccd24..a040bdd99 100644
--- a/modules/cql/src/blaze/elm/compiler/macros.clj
+++ b/modules/cql/src/blaze/elm/compiler/macros.clj
@@ -1,38 +1,82 @@
 (ns blaze.elm.compiler.macros
   (:require
+    [blaze.async.comp :as ac]
+    [blaze.db.api :as d]
     [blaze.elm.compiler.core :as core]
-    [blaze.elm.expression.cache :as-alias expr-cache]))
+    [blaze.elm.compiler.expr-cache :as ec]
+    [blaze.elm.compiler.external-data :as ed]
+    [blaze.elm.expression :as expr]
+    [clojure.spec.alpha :as s]
+    [prometheus.alpha :as prom :refer [defcounter defhistogram]]
+    [taoensso.timbre :as log])
+  (:import
+    [com.github.benmanes.caffeine.cache AsyncCache]
+    [java.util.function BiFunction]))
 
 
 (set! *warn-on-reflection* true)
 
 
-(defn- compile-kw [name]
-  (keyword "elm.compiler.type" (clojure.core/name name)))
+(defhistogram bloom-filter-creation-duration-seconds
+  "Durations in Cassandra resource store."
+  {:namespace "blaze"
+   :subsystem "cql_expr_cache"}
+  (take 14 (iterate #(* 2 %) 0.1)))
+
+
+(defcounter bloom-filter-useful-total
+  "Number of times bloom filter has avoided expression evaluation."
+  {:namespace "blaze"
+   :subsystem "cql_expr_cache"})
+
+
+(defcounter bloom-filter-not-useful-total
+  "Number of times bloom filter has not avoided expression evaluation."
+  {:namespace "blaze"
+   :subsystem "cql_expr_cache"})
 
 
-(defn generate-binding-vector
+(defcounter bloom-filter-false-positive-total
+  "Number of false positives reported by Bloom all filters."
+  {:namespace "blaze"
+   :subsystem "cql_expr_cache"})
+
+
+(defn- generate-binding-vector
   "Creates a binding vector of at least `[operand-binding operand]` and
-  optionally `[operand-binding operand expr-binding expr-sym]` if `expr-binding`
-  is given."
-  [operand-binding operand expr-binding expr-sym]
-  (cond-> [operand-binding operand] expr-binding (conj expr-binding expr-sym)))
-
-
-(defn generate-unop [name operand-sym operand-binding expr-binding expr-sym body]
-  (let [context-sym (gensym "context")
-        resource-sym (gensym "resource")
-        scope-sym (gensym "scope")]
-    `(reify core/Expression
-       (~'-static [~'_]
-         false)
-       (~'-eval [~'_ ~context-sym ~resource-sym ~scope-sym]
-         (let ~(generate-binding-vector
-                 operand-binding `(core/-eval ~operand-sym ~context-sym ~resource-sym ~scope-sym)
-                 expr-binding expr-sym)
-           ~@body))
-       (~'-form [~'_]
-         (list (quote ~name) (core/-form ~operand-sym))))))
+  optionally `[operand-binding operand elm-elm-expr-binding elm-expr]` if
+  `elm-elm-expr-binding` is given."
+  [operand-binding operand elm-expr-binding elm-expr]
+  (cond-> [operand-binding operand] elm-expr-binding (conj elm-expr-binding elm-expr)))
+
+
+(defn get-cache [{::expr/keys [cache] :as context} eval-context expr]
+  (let [cache (.get ^AsyncCache cache (expr/hash expr)
+                    (reify BiFunction
+                      (apply [_ _ executor]
+                        (ac/supply-async
+                          #(let [db (:db context)]
+                             (log/debug "create Bloom filter for expression"
+                                        (core/-form expr)
+                                        "evaluating it for all"
+                                        eval-context
+                                        "resources")
+                             (with-open [_ (prom/timer bloom-filter-creation-duration-seconds)]
+                               (ec/cache
+                                 (d/t db)
+                                 (into
+                                   []
+                                   (comp (map (partial ed/mk-resource db))
+                                         (filter (partial expr/eval context expr))
+                                         (map :id))
+                                   (d/type-list db eval-context)))))
+                          executor))))]
+    (when (.isDone cache)
+      (.get cache))))
+
+
+(defn- compile-kw [name]
+  (keyword "elm.compiler.type" (clojure.core/name name)))
 
 
 (defmacro defunop
@@ -40,18 +84,142 @@
   [name & more]
   (let [attr-map (when (map? (first more)) (first more))
         more (if (map? (first more)) (next more) more)
-        [[operand-binding expr-binding] & body] more
-        context-sym (gensym "context")
-        operand-sym (gensym "operand")
-        expr-sym (gensym "expr")]
-    `(defmethod core/compile* ~(compile-kw name)
-       [~context-sym ~expr-sym]
-       (let [~operand-sym (core/compile* (merge ~context-sym ~(dissoc attr-map :cache)) (:operand ~expr-sym))]
-         (if (core/static? ~operand-sym)
-           (let [~operand-binding ~operand-sym
-                 ~(or expr-binding '_) ~expr-sym]
-             ~@body)
-           ~(generate-unop name operand-sym operand-binding expr-binding expr-sym body))))))
+        [[operand-binding elm-expr-binding] & body] more
+        elm-expr (gensym "elm-expr")
+        operand (gensym "operand")
+        context (gensym "context")
+        eval-context (gensym "eval-context")
+        resource (gensym "resource")
+        scope (gensym "scope")
+        cache (gensym "cache")
+        expr (gensym "expr")]
+    `(do
+       ~(if (:cache attr-map)
+          `(do
+             (declare ~(symbol (str name "-caching-op")))
+
+             (s/fdef ~(symbol (str name "-cache-op"))
+               :args ~(if elm-expr-binding
+                        `(s/cat :operand core/expr?
+                                :eval-context string?
+                                :cache ec/cache?
+                                :expr :elm/expression)
+                        `(s/cat :operand core/expr?
+                                :eval-context string?
+                                :cache ec/cache?))
+               :ret core/expr?)
+
+             (defn ~(symbol (str name "-cache-op"))
+               ~(cond-> [operand eval-context cache] elm-expr-binding (conj elm-expr))
+               (reify core/Expression
+                 (~'-static [~'_]
+                   false)
+                 (~'-attach-cache [~expr ~context]
+                   (if-let [~cache (get-cache ~context ~eval-context ~expr)]
+                     ~(if elm-expr-binding
+                        `(~(symbol (str name "-cache-op"))
+                           (core/-attach-cache ~operand ~context)
+                           ~eval-context ~cache ~elm-expr)
+                        `(~(symbol (str name "-cache-op"))
+                           (core/-attach-cache ~operand ~context)
+                           ~eval-context ~cache))
+                     ~(if elm-expr-binding
+                        `(~(symbol (str name "-caching-op"))
+                           (core/-attach-cache ~operand ~context)
+                           ~eval-context ~elm-expr)
+                        `(~(symbol (str name "-caching-op"))
+                           (core/-attach-cache ~operand ~context)
+                           ~eval-context))))
+                 (~'-eval [~'_ ~context ~resource ~scope]
+                   (if (ec/might-contain? ~cache ~resource)
+                     (let [res# (let ~(generate-binding-vector
+                                        operand-binding `(core/-eval ~operand
+                                                                     ~context
+                                                                     ~resource
+                                                                     ~scope)
+                                        elm-expr-binding elm-expr)
+                                  ~@body)]
+                       (prom/inc! bloom-filter-not-useful-total)
+                       (when-not res#
+                         (prom/inc! bloom-filter-false-positive-total))
+                       res#)
+                     (do (prom/inc! bloom-filter-useful-total)
+                         false)))
+                 (~'-form [~'_]
+                   (list (quote ~name) (core/-form ~operand)))))
+
+             (s/fdef ~(symbol (str name "-caching-op"))
+               :args ~(if elm-expr-binding
+                        `(s/cat :operand core/expr?
+                                :eval-context string?
+                                :expr :elm/expression)
+                        `(s/cat :operand core/expr? :eval-context string?))
+               :ret core/expr?)
+
+             (defn ~(symbol (str name "-caching-op"))
+               ~(cond-> [operand eval-context] elm-expr-binding (conj elm-expr))
+               (reify core/Expression
+                 (~'-static [~'_]
+                   false)
+                 (~'-attach-cache [~expr ~context]
+                   (if-let [~cache (get-cache ~context ~eval-context ~expr)]
+                     ~(if elm-expr-binding
+                        `(~(symbol (str name "-cache-op"))
+                           (core/-attach-cache ~operand ~context)
+                           ~eval-context ~cache ~elm-expr)
+                        `(~(symbol (str name "-cache-op"))
+                           (core/-attach-cache ~operand ~context)
+                           ~eval-context ~cache))
+                     ~(if elm-expr-binding
+                        `(~(symbol (str name "-caching-op"))
+                           (core/-attach-cache ~operand ~context)
+                           ~eval-context ~elm-expr)
+                        `(~(symbol (str name "-caching-op"))
+                           (core/-attach-cache ~operand ~context)
+                           ~eval-context))))
+                 (~'-eval [~'_ ~context ~resource ~scope]
+                   (let ~(generate-binding-vector
+                           operand-binding `(core/-eval ~operand ~context ~resource ~scope)
+                           elm-expr-binding elm-expr)
+                     ~@body))
+                 (~'-form [~'_]
+                   (list (quote ~name) (core/-form ~operand))))))
+
+          `(defn ~(symbol (str name "-op"))
+             ~(cond-> [operand] elm-expr-binding (conj elm-expr))
+             (reify core/Expression
+               (~'-static [~'_]
+                 false)
+               (~'-attach-cache [~'_ ~context]
+                 ~(if elm-expr-binding
+                    `(~(symbol (str name "-op"))
+                       (core/-attach-cache ~operand ~context) ~elm-expr)
+                    `(~(symbol (str name "-op"))
+                       (core/-attach-cache ~operand ~context))))
+               (~'-eval [~'_ ~context ~resource ~scope]
+                 (let ~(generate-binding-vector
+                         operand-binding `(core/-eval ~operand ~context ~resource ~scope)
+                         elm-expr-binding elm-expr)
+                   ~@body))
+               (~'-form [~'_]
+                 (list (quote ~name) (core/-form ~operand))))))
+
+       (defmethod core/compile* ~(compile-kw name)
+         [{~eval-context :eval-context :as ~context}
+          {~operand :operand :as ~elm-expr}]
+         (let [~operand (core/compile* (merge ~context ~(dissoc attr-map :cache)) ~operand)]
+           (if (core/static? ~operand)
+             (let ~(generate-binding-vector
+                     operand-binding operand
+                     elm-expr-binding elm-expr)
+               ~@body)
+             ~(if (:cache attr-map)
+                (if elm-expr-binding
+                  `(~(symbol (str name "-caching-op")) ~operand ~eval-context ~elm-expr)
+                  `(~(symbol (str name "-caching-op")) ~operand ~eval-context))
+                (if elm-expr-binding
+                  `(~(symbol (str name "-op")) ~operand ~elm-expr)
+                  `(~(symbol (str name "-op")) ~operand)))))))))
 
 
 (defmacro defbinop
@@ -59,25 +227,35 @@
   [name & more]
   (let [attr-map (when (map? (first more)) (first more))
         more (if (map? (first more)) (next more) more)
-        [[op-1-binding op-2-binding] & body] more]
-    `(defmethod core/compile* ~(compile-kw name)
-       [context# {[operand-1# operand-2#] :operand}]
-       (let [context# (merge context# ~attr-map)
-             operand-1# (core/compile* context# operand-1#)
-             operand-2# (core/compile* context# operand-2#)]
-         (if (and (core/static? operand-1#) (core/static? operand-2#))
-           (let [~op-1-binding operand-1#
-                 ~op-2-binding operand-2#]
-             ~@body)
-           (reify core/Expression
-             (~'-static [~'_]
-               false)
-             (~'-eval [~'_ context# resource# scope#]
-               (let [~op-1-binding (core/-eval operand-1# context# resource# scope#)
-                     ~op-2-binding (core/-eval operand-2# context# resource# scope#)]
-                 ~@body))
-             (~'-form [~'_]
-               (list (quote ~name) (core/-form operand-1#) (core/-form operand-2#)))))))))
+        [[op-1-binding op-2-binding] & body] more
+        context (gensym "context")
+        op-1 (gensym "op-1")
+        op-2 (gensym "op-2")]
+    `(do
+       (defn ~(symbol (str name "-op")) [~op-1 ~op-2]
+         (reify core/Expression
+           (~'-static [~'_]
+             false)
+           (~'-attach-cache [~'_ ~'cache]
+             (~(symbol (str name "-op"))
+               (core/-attach-cache ~op-1 ~'cache)
+               (core/-attach-cache ~op-2 ~'cache)))
+           (~'-eval [~'_ context# resource# scope#]
+             (let [~op-1-binding (core/-eval ~op-1 context# resource# scope#)
+                   ~op-2-binding (core/-eval ~op-2 context# resource# scope#)]
+               ~@body))
+           (~'-form [~'_]
+             (list (quote ~name) (core/-form ~op-1) (core/-form ~op-2)))))
+       (defmethod core/compile* ~(compile-kw name)
+         [~context {[~op-1 ~op-2] :operand}]
+         (let [context# ~(if attr-map `(merge ~context ~attr-map) context)
+               ~op-1 (core/compile* context# ~op-1)
+               ~op-2 (core/compile* context# ~op-2)]
+           (if (and (core/static? ~op-1) (core/static? ~op-2))
+             (let [~op-1-binding ~op-1
+                   ~op-2-binding ~op-2]
+               ~@body)
+             (~(symbol (str name "-op")) ~op-1 ~op-2)))))))
 
 
 (defmacro defternop
@@ -104,33 +282,42 @@
 (defmacro defnaryop
   {:arglists '([name bindings & body])}
   [name [operands-binding] & body]
-  `(defmethod core/compile* ~(compile-kw name)
-     [context# {operands# :operand}]
-     (let [operands# (mapv #(core/compile* context# %) operands#)]
+  `(do
+     (defn ~(symbol (str name "-op")) [~operands-binding]
        (reify core/Expression
          (~'-static [~'_]
            false)
+         (~'-attach-cache [~'_ ~'cache]
+           (~(symbol (str name "-op"))
+             (mapv #(core/-attach-cache % ~'cache) ~operands-binding)))
          (~'-eval [~'_ context# resource# scope#]
-           (let [~operands-binding (mapv #(core/-eval % context# resource# scope#) operands#)]
+           (let [~operands-binding (mapv #(core/-eval % context# resource# scope#) ~operands-binding)]
              ~@body))
          (~'-form [~'_]
-           (cons (quote ~name) (map core/-form operands#)))))))
+           (cons (quote ~name) (map core/-form ~operands-binding)))))
+     (defmethod core/compile* ~(compile-kw name)
+       [context# {operands# :operand}]
+       (~(symbol (str name "-op")) (mapv #(core/compile* context# %) operands#)))))
 
 
 (defmacro defaggop
   {:arglists '([name bindings & body])}
   [name [source-binding] & body]
-  `(defmethod core/compile* ~(compile-kw name)
-     [context# {source# :source}]
-     (let [source# (core/compile* context# source#)]
+  `(do
+     (defn ~(symbol (str name "-op")) [~source-binding]
        (reify core/Expression
          (~'-static [~'_]
            false)
+         (~'-attach-cache [~'_ ~'cache]
+           (~(symbol (str name "-op")) (core/-attach-cache ~source-binding ~'cache)))
          (~'-eval [~'_ context# resource# scope#]
-           (let [~source-binding (core/-eval source# context# resource# scope#)]
+           (let [~source-binding (core/-eval ~source-binding context# resource# scope#)]
              ~@body))
          (~'-form [~'_]
-           (list (quote ~name) (core/-form source#)))))))
+           (list (quote ~name) (core/-form ~source-binding)))))
+     (defmethod core/compile* ~(compile-kw name)
+       [context# {source# :source}]
+       (~(symbol (str name "-op")) (core/compile* context# source#)))))
 
 
 (defmacro defunopp
@@ -156,26 +343,37 @@
   [name & more]
   (let [attr-map (when (map? (first more)) (first more))
         more (if (map? (first more)) (next more) more)
-        [[op-1-binding op-2-binding precision-binding] & body] more]
-    `(defmethod core/compile* ~(compile-kw name)
-       [context# {[operand-1# operand-2#] :operand precision# :precision}]
-       (let [context# (merge context# ~attr-map)
-             operand-1# (core/compile* context# operand-1#)
-             operand-2# (core/compile* context# operand-2#)
-             chrono-precision# (some-> precision# core/to-chrono-unit)]
-         (if (and (core/static? operand-1#) (core/static? operand-2#))
-           (let [~op-1-binding operand-1#
-                 ~op-2-binding operand-2#
-                 ~precision-binding chrono-precision#]
-             ~@body)
-           (reify core/Expression
-             (~'-static [~'_]
-               false)
-             (~'-eval [~'_ context# resource# scope#]
-               (let [~op-1-binding (core/-eval operand-1# context# resource# scope#)
-                     ~op-2-binding (core/-eval operand-2# context# resource# scope#)
-                     ~precision-binding chrono-precision#]
-                 ~@body))
-             (~'-form [~'_]
-               (list (quote ~name) (core/-form operand-1#) (core/-form operand-2#)
-                     precision#))))))))
+        [[op-1-binding op-2-binding precision-binding] & body] more
+        context (gensym "context")
+        op-1 (gensym "op-1")
+        op-2 (gensym "op-2")
+        precision (gensym "precision")]
+    `(do
+       (defn ~(symbol (str name "-op")) [~op-1 ~op-2 ~precision-binding ~precision]
+         (reify core/Expression
+           (~'-static [~'_]
+             false)
+           (~'-attach-cache [~'_ ~'context]
+             (~(symbol (str name "-op"))
+               (core/-attach-cache ~op-1 ~'context)
+               (core/-attach-cache ~op-2 ~'context)
+               ~precision-binding ~precision))
+           (~'-eval [~'_ context# resource# scope#]
+             (let [~op-1-binding (core/-eval ~op-1 context# resource# scope#)
+                   ~op-2-binding (core/-eval ~op-2 context# resource# scope#)]
+               ~@body))
+           (~'-form [~'_]
+             (list (quote ~name) (core/-form ~op-1) (core/-form ~op-2)
+                   ~precision))))
+       (defmethod core/compile* ~(compile-kw name)
+         [~context {[~op-1 ~op-2] :operand ~precision :precision}]
+         (let [context# ~(if attr-map `(merge ~context ~attr-map) context)
+               ~op-1 (core/compile* context# ~op-1)
+               ~op-2 (core/compile* context# ~op-2)
+               ~precision-binding (some-> ~precision core/to-chrono-unit)]
+           (if (and (core/static? ~op-1) (core/static? ~op-2))
+             (let [~op-1-binding ~op-1
+                   ~op-2-binding ~op-2]
+               ~@body)
+             (~(symbol (str name "-op")) ~op-1 ~op-2
+               ~precision-binding ~precision)))))))
diff --git a/modules/cql/src/blaze/elm/compiler/queries.clj b/modules/cql/src/blaze/elm/compiler/queries.clj
index b05f6a819..a28453524 100644
--- a/modules/cql/src/blaze/elm/compiler/queries.clj
+++ b/modules/cql/src/blaze/elm/compiler/queries.clj
@@ -135,37 +135,35 @@
         return-xform-factory))))
 
 
-(defrecord EductionQueryExpression [xform-factory source]
-  core/Expression
-  (-static [_]
-    false)
-  (-eval [_ context resource scope]
-    (coll/eduction
-      (-create xform-factory context resource scope)
-      (core/-eval source context resource scope)))
-  (-form [_]
-    `(~'eduction-query ~(-form xform-factory) ~(core/-form source))))
-
-
 (defn- eduction-expr [xform-factory source]
-  (->EductionQueryExpression xform-factory source))
-
-
-(defrecord IntoVectorQueryExpression [xform-factory source]
-  core/Expression
-  (-static [_]
-    false)
-  (-eval [_ context resource scope]
-    (into
-      []
-      (-create xform-factory context resource scope)
-      (core/-eval source context resource scope)))
-  (-form [_]
-    `(~'vector-query ~(-form xform-factory) ~(core/-form source))))
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      ;;TODO: attach cache to xform-factory
+      (eduction-expr xform-factory (core/-attach-cache source context)))
+    (-eval [_ context resource scope]
+      (coll/eduction
+        (-create xform-factory context resource scope)
+        (core/-eval source context resource scope)))
+    (-form [_]
+      `(~'eduction-query ~(-form xform-factory) ~(core/-form source)))))
 
 
 (defn- into-vector-expr [xform-factory source]
-  (->IntoVectorQueryExpression xform-factory source))
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      ;;TODO: attach cache to xform-factory
+      (into-vector-expr xform-factory (core/-attach-cache source context)))
+    (-eval [_ context resource scope]
+      (into
+        []
+        (-create xform-factory context resource scope)
+        (core/-eval source context resource scope)))
+    (-form [_]
+      `(~'vector-query ~(-form xform-factory) ~(core/-form source)))))
 
 
 (deftype AscComparator []
@@ -202,45 +200,56 @@
   (if (#{"desc" "descending"} direction) desc-comparator asc-comparator))
 
 
-(defrecord SortQueryExpression [source sort-by-item]
-  core/Expression
-  (-static [_]
-    false)
-  (-eval [_ context resource scope]
-    ;; TODO: build a comparator of all sort by items
-    (->> (vec (core/-eval source context resource scope))
-         (sort-by
-           (if-let [expr (:expression sort-by-item)]
-             #(core/-eval expr context resource %)
-             identity)
-           (comparator (:direction sort-by-item)))
-         (vec))))
+(defn sort-by-item-form [sort-by-item]
+  (if-let [expr (:expression sort-by-item)]
+    [(symbol (:direction sort-by-item)) (core/-form expr)]
+    (symbol (:direction sort-by-item))))
 
 
 (defn sort-expr [source sort-by-item]
-  (->SortQueryExpression source sort-by-item))
-
-
-(defrecord XformSortQueryExpression [xform-factory source sort-by-item]
-  core/Expression
-  (-static [_]
-    false)
-  (-eval [_ context resource scope]
-    ;; TODO: build a comparator of all sort by items
-    (->> (into
-           []
-           (-create xform-factory context resource scope)
-           (core/-eval source context resource scope))
-         (sort-by
-           (if-let [expr (:expression sort-by-item)]
-             #(core/-eval expr context resource %)
-             identity)
-           (comparator (:direction sort-by-item)))
-         (vec))))
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (sort-expr (core/-attach-cache source context)
+                 (update sort-by-item :expression core/-attach-cache context)))
+    (-eval [_ context resource scope]
+      ;; TODO: build a comparator of all sort by items
+      (->> (vec (core/-eval source context resource scope))
+           (sort-by
+             (if-let [expr (:expression sort-by-item)]
+               #(core/-eval expr context resource %)
+               identity)
+             (comparator (:direction sort-by-item)))
+           (vec)))
+    (-form [_]
+      `(~'sorted-vector-query ~(core/-form source)
+         ~(sort-by-item-form sort-by-item)))))
 
 
 (defn xform-sort-expr [xform-factory source sort-by-item]
-  (->XformSortQueryExpression xform-factory source sort-by-item))
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      ;;TODO: attach cache to xform-factory
+      (xform-sort-expr xform-factory (core/-attach-cache source context)
+                       (update sort-by-item :expression core/-attach-cache context)))
+    (-eval [_ context resource scope]
+      ;; TODO: build a comparator of all sort by items
+      (->> (into
+             []
+             (-create xform-factory context resource scope)
+             (core/-eval source context resource scope))
+           (sort-by
+             (if-let [expr (:expression sort-by-item)]
+               #(core/-eval expr context resource %)
+               identity)
+             (comparator (:direction sort-by-item)))
+           (vec)))
+    (-form [_]
+      `(~'sorted-vector-query ~(-form xform-factory) ~(core/-form source)
+         ~(sort-by-item-form sort-by-item)))))
 
 
 (declare compile-with-equiv-clause)
@@ -312,6 +321,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [expr _]
+    expr)
   (-eval [_ _ _ scopes]
     (get scopes key))
   (-form [_]
diff --git a/modules/cql/src/blaze/elm/compiler/reusing_logic.clj b/modules/cql/src/blaze/elm/compiler/reusing_logic.clj
index 0534253d6..e55a9663c 100644
--- a/modules/cql/src/blaze/elm/compiler/reusing_logic.clj
+++ b/modules/cql/src/blaze/elm/compiler/reusing_logic.clj
@@ -33,6 +33,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [expr _]
+    expr)
   (-eval [_ {:keys [expression-defs] :as context} resource _]
     (if-let [{:keys [expression]} (get expression-defs name)]
       (core/-eval expression context resource nil)
@@ -74,6 +76,8 @@
         (reify core/Expression
           (-static [_]
             false)
+          (-attach-cache [expr _]
+            expr)
           (-eval [_ {:keys [db expression-defs] :as context} _ _]
             (if-some [{:keys [expression]} (get expression-defs name)]
               (mapv
@@ -110,6 +114,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [_ context]
+    (->ToQuantityFunctionExpression (core/-attach-cache operand context)))
   (-eval [_ context resource scope]
     (-to-quantity (core/-eval operand context resource scope)))
   (-form [_]
@@ -120,6 +126,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [_ context]
+    (->ToCodeFunctionExpression (core/-attach-cache operand context)))
   (-eval [_ context resource scope]
     (let [{:keys [system version code]} (core/-eval operand context resource scope)]
       (code/to-code (type/value system) (type/value version) (type/value code))))
@@ -131,6 +139,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [_ context]
+    (->ToDateFunctionExpression (core/-attach-cache operand context)))
   (-eval [_ context resource scope]
     (type/value (core/-eval operand context resource scope)))
   (-form [_]
@@ -141,6 +151,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [_ context]
+    (->ToDateTimeFunctionExpression (core/-attach-cache operand context)))
   (-eval [_ {:keys [now] :as context} resource scope]
     (p/to-date-time (type/value (core/-eval operand context resource scope)) now))
   (-form [_]
@@ -151,6 +163,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [_ context]
+    (->ToStringFunctionExpression (core/-attach-cache operand context)))
   (-eval [_ context resource scope]
     (some-> (type/value (core/-eval operand context resource scope)) str))
   (-form [_]
@@ -176,6 +190,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [_ context]
+    (->ToIntervalFunctionExpression (core/-attach-cache operand context)))
   (-eval [_ context resource scope]
     (-to-interval (core/-eval operand context resource scope) context))
   (-form [_]
@@ -230,6 +246,8 @@
   (reify core/Expression
     (-static [_]
       false)
+    (-attach-cache [expr _]
+      expr)
     (-eval [_ _ _ scope]
       (scope name))
     (-form [_]
diff --git a/modules/cql/src/blaze/elm/compiler/spec.clj b/modules/cql/src/blaze/elm/compiler/spec.clj
index 896730d14..23915e68a 100644
--- a/modules/cql/src/blaze/elm/compiler/spec.clj
+++ b/modules/cql/src/blaze/elm/compiler/spec.clj
@@ -1,18 +1,24 @@
 (ns blaze.elm.compiler.spec
   (:require
     [blaze.db.spec]
+    [blaze.elm.compiler :as-alias c]
     [blaze.elm.compiler.core :as core]
     [blaze.elm.spec]
+    [blaze.fhir.spec.spec]
     [clojure.spec.alpha :as s]))
 
 
-(s/def :blaze.elm.compiler/expression
+(s/def ::c/expression
   core/expr?)
 
 
-(s/def :blaze.elm.compiler/function
+(s/def ::c/function
   fn?)
 
 
+(s/def ::c/eval-context
+  (s/or :unfiltered #{"Unfiltered"} :resource-type :fhir.resource/type))
+
+
 (s/def :elm/compile-context
-  (s/keys :req-un [:elm/library :blaze.db/node]))
+  (s/keys :req-un [:elm/library ::c/eval-context :blaze.db/node]))
diff --git a/modules/cql/src/blaze/elm/compiler/string_operators.clj b/modules/cql/src/blaze/elm/compiler/string_operators.clj
index 7ee4c1d17..74b4e8646 100644
--- a/modules/cql/src/blaze/elm/compiler/string_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/string_operators.clj
@@ -15,28 +15,40 @@
 
 
 ;; 17.1. Combine
+(defn combine-op
+  ([source]
+   (reify core/Expression
+     (-static [_]
+       false)
+     (-attach-cache [_ context]
+       (combine-op (core/-attach-cache source context)))
+     (-eval [_ context resource scope]
+       (when-let [source (core/-eval source context resource scope)]
+         (string/combine source)))
+     (-form [_]
+       (list 'combine (core/-form source)))))
+  ([source separator]
+   (reify core/Expression
+     (-static [_]
+       false)
+     (-attach-cache [_ context]
+       (combine-op (core/-attach-cache source context)
+                   (core/-attach-cache separator context)))
+     (-eval [_ context resource scope]
+       (when-let [source (core/-eval source context resource scope)]
+         (string/combine (core/-eval separator context resource scope)
+                         source)))
+     (-form [_]
+       (list 'combine (core/-form source) (core/-form separator))))))
+
+
 (defmethod core/compile* :elm.compiler.type/combine
   [context {:keys [source separator]}]
   (let [source (core/compile* context source)
         separator (some->> separator (core/compile* context))]
     (if separator
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (when-let [source (core/-eval source context resource scope)]
-            (string/combine (core/-eval separator context resource scope)
-                            source)))
-        (-form [_]
-          (list 'combine (core/-form source) (core/-form separator))))
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (when-let [source (core/-eval source context resource scope)]
-            (string/combine source)))
-        (-form [_]
-          (list 'combine (core/-form source)))))))
+      (combine-op source separator)
+      (combine-op source))))
 
 
 ;; 17.2. Concatenate
@@ -56,19 +68,22 @@
 
 
 ;; 17.7. LastPositionOf
+(defn last-position-of-op [pattern string]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-eval [_ context resource scope]
+      (when-let [^String pattern (core/-eval pattern context resource scope)]
+        (when-let [^String string (core/-eval string context resource scope)]
+          (.lastIndexOf string pattern))))
+    (-form [_]
+      (list 'last-position-of (core/-form pattern) (core/-form string)))))
+
+
 (defmethod core/compile* :elm.compiler.type/last-position-of
   [context {:keys [pattern string]}]
-  (let [pattern (core/compile* context pattern)
-        string (core/compile* context string)]
-    (reify core/Expression
-      (-static [_]
-        false)
-      (-eval [_ context resource scope]
-        (when-let [^String pattern (core/-eval pattern context resource scope)]
-          (when-let [^String string (core/-eval string context resource scope)]
-            (.lastIndexOf string pattern))))
-      (-form [_]
-        (list 'last-position-of (core/-form pattern) (core/-form string))))))
+  (last-position-of-op (core/compile* context pattern)
+                       (core/compile* context string)))
 
 
 ;; 17.8. Length
@@ -88,19 +103,22 @@
 
 
 ;; 17.12. PositionOf
+(defn position-of-op [pattern string]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-eval [_ context resource scope]
+      (when-let [^String pattern (core/-eval pattern context resource scope)]
+        (when-let [^String string (core/-eval string context resource scope)]
+          (.indexOf string pattern))))
+    (-form [_]
+      (list 'position-of (core/-form pattern) (core/-form string)))))
+
+
 (defmethod core/compile* :elm.compiler.type/position-of
   [context {:keys [pattern string]}]
-  (let [pattern (core/compile* context pattern)
-        string (core/compile* context string)]
-    (reify core/Expression
-      (-static [_]
-        false)
-      (-eval [_ context resource scope]
-        (when-let [^String pattern (core/-eval pattern context resource scope)]
-          (when-let [^String string (core/-eval string context resource scope)]
-            (.indexOf string pattern))))
-      (-form [_]
-        (list 'position-of (core/-form pattern) (core/-form string))))))
+  (position-of-op (core/compile* context pattern)
+                  (core/compile* context string)))
 
 
 ;; 17.13. ReplaceMatches
@@ -110,46 +128,58 @@
 
 
 ;; 17.14. Split
+(defn- split-op
+  ([string]
+   (reify core/Expression
+     (-static [_]
+       false)
+     (-attach-cache [_ context]
+       (split-op (core/-attach-cache string context)))
+     (-eval [_ context resource scope]
+       (when-let [string (core/-eval string context resource scope)]
+         [string]))
+     (-form [_]
+       (list 'split (core/-form string)))))
+  ([string separator]
+   (reify core/Expression
+     (-static [_]
+       false)
+     (-attach-cache [_ context]
+       (split-op (core/-attach-cache string context)
+                 (core/-attach-cache separator context)))
+     (-eval [_ context resource scope]
+       (when-let [string (core/-eval string context resource scope)]
+         (if (= "" string)
+           [string]
+           (if-let [separator (core/-eval separator context resource scope)]
+             (case (count separator)
+               0
+               [string]
+               1
+               (loop [[char & more] string
+                      result []
+                      acc (StringBuilder.)]
+                 (if (= (str char) separator)
+                   (if more
+                     (recur more (conj result (str acc)) (StringBuilder.))
+                     (conj result (str acc)))
+                   (if more
+                     (recur more result (.append acc char))
+                     (conj result (str (.append acc char))))))
+               ;; TODO: implement split with more than one char.
+               (throw (Exception. "TODO: implement split with separators longer than one char.")))
+             [string]))))
+     (-form [_]
+       (list 'split (core/-form string) (core/-form separator))))))
+
+
 (defmethod core/compile* :elm.compiler.type/split
   [context {string :stringToSplit :keys [separator]}]
   (let [string (core/compile* context string)
         separator (some->> separator (core/compile* context))]
     (if separator
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (when-let [string (core/-eval string context resource scope)]
-            (if (= "" string)
-              [string]
-              (if-let [separator (core/-eval separator context resource scope)]
-                (case (count separator)
-                  0
-                  [string]
-                  1
-                  (loop [[char & more] string
-                         result []
-                         acc (StringBuilder.)]
-                    (if (= (str char) separator)
-                      (if more
-                        (recur more (conj result (str acc)) (StringBuilder.))
-                        (conj result (str acc)))
-                      (if more
-                        (recur more result (.append acc char))
-                        (conj result (str (.append acc char))))))
-                  ;; TODO: implement split with more than one char.
-                  (throw (Exception. "TODO: implement split with separators longer than one char.")))
-                [string]))))
-        (-form [_]
-          (list 'split (core/-form string) (core/-form separator))))
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (when-let [string (core/-eval string context resource scope)]
-            [string]))
-        (-form [_]
-          (list 'split (core/-form string)))))))
+      (split-op string separator)
+      (split-op string))))
 
 
 ;; 17.16. StartsWith
@@ -159,34 +189,40 @@
 
 
 ;; 17.17. Substring
+(defn substring-op
+  ([string start-index]
+   (reify core/Expression
+     (-static [_]
+       false)
+     (-eval [_ context resource scope]
+       (when-let [^String string (core/-eval string context resource scope)]
+         (when-let [start-index (core/-eval start-index context resource scope)]
+           (when (and (<= 0 start-index) (< start-index (count string)))
+             (subs string start-index)))))
+     (-form [_]
+       (list 'substring (core/-form string) (core/-form start-index)))))
+  ([string start-index length]
+   (reify core/Expression
+     (-static [_]
+       false)
+     (-eval [_ context resource scope]
+       (when-let [^String string (core/-eval string context resource scope)]
+         (when-let [start-index (core/-eval start-index context resource scope)]
+           (when (and (<= 0 start-index) (< start-index (count string)))
+             (subs string start-index (min (+ start-index length)
+                                           (count string)))))))
+     (-form [_]
+       (list 'substring (core/-form string) (core/-form start-index)
+             (core/-form length))))))
+
 (defmethod core/compile* :elm.compiler.type/substring
   [context {string :stringToSub start-index :startIndex :keys [length]}]
   (let [string (core/compile* context string)
         start-index (core/compile* context start-index)
         length (some->> length (core/compile* context))]
     (if length
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (when-let [^String string (core/-eval string context resource scope)]
-            (when-let [start-index (core/-eval start-index context resource scope)]
-              (when (and (<= 0 start-index) (< start-index (count string)))
-                (subs string start-index (min (+ start-index length)
-                                              (count string)))))))
-        (-form [_]
-          (list 'substring (core/-form string) (core/-form start-index)
-                (core/-form length))))
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (when-let [^String string (core/-eval string context resource scope)]
-            (when-let [start-index (core/-eval start-index context resource scope)]
-              (when (and (<= 0 start-index) (< start-index (count string)))
-                (subs string start-index)))))
-        (-form [_]
-          (list 'substring (core/-form string) (core/-form start-index)))))))
+      (substring-op string start-index length)
+      (substring-op string start-index))))
 
 
 ;; 17.18. Upper
diff --git a/modules/cql/src/blaze/elm/compiler/structured_values.clj b/modules/cql/src/blaze/elm/compiler/structured_values.clj
index 0b649a208..4f81c3491 100644
--- a/modules/cql/src/blaze/elm/compiler/structured_values.clj
+++ b/modules/cql/src/blaze/elm/compiler/structured_values.clj
@@ -47,26 +47,35 @@
     elements))
 
 
+(defn tuple [elements]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (tuple
+        (reduce-kv
+          (fn [r key value]
+            (assoc r key (core/-attach-cache value context)))
+          {}
+          elements)))
+    (-eval [_ context resource scope]
+      (reduce-kv
+        (fn [r key value]
+          (assoc r key (core/-eval value context resource scope)))
+        {}
+        elements))
+    (-form [_]
+      (reduce-kv
+        (fn [r key value]
+          (assoc r key (core/-form value)))
+        {}
+        elements))))
+
+
 (defmethod core/compile* :elm.compiler.type/tuple
   [context {elements :element}]
   (let [elements (compile-elements context elements)]
-    (if (every? core/static? (vals elements))
-      elements
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (reduce-kv
-            (fn [r key value]
-              (assoc r key (core/-eval value context resource scope)))
-            {}
-            elements))
-        (-form [_]
-          (reduce-kv
-            (fn [r key value]
-              (assoc r key (core/-form value)))
-            {}
-            elements))))))
+    (cond-> elements (some (comp not core/static?) (vals elements)) tuple)))
 
 
 ;; 2.2. Instance
@@ -85,6 +94,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [_ context]
+    (->SourcePropertyExpression (core/-attach-cache source context) key))
   (-eval [_ context resource scope]
     (p/get (core/-eval source context resource scope) key))
   (-form [_]
@@ -95,6 +106,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [_ context]
+    (->SourcePropertyValueExpression (core/-attach-cache source context) key))
   (-eval [_ context resource scope]
     (type/value (p/get (core/-eval source context resource scope) key)))
   (-form [_]
@@ -105,6 +118,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [expr _]
+    expr)
   (-eval [_ _ _ value]
     (p/get value key))
   (-form [_]
@@ -115,6 +130,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [expr _]
+    expr)
   (-eval [_ _ _ scope]
     (p/get (get scope scope-key) key))
   (-form [_]
@@ -125,6 +142,8 @@
   core/Expression
   (-static [_]
     false)
+  (-attach-cache [expr _]
+    expr)
   (-eval [_ _ _ scope]
     (type/value (p/get (get scope scope-key) key)))
   (-form [_]
diff --git a/modules/cql/src/blaze/elm/compiler/type_operators.clj b/modules/cql/src/blaze/elm/compiler/type_operators.clj
index 2ddbae60c..9365fc504 100644
--- a/modules/cql/src/blaze/elm/compiler/type_operators.clj
+++ b/modules/cql/src/blaze/elm/compiler/type_operators.clj
@@ -78,19 +78,25 @@
         :expression expression))))
 
 
+(defn as-op [type pred operand]
+  (reify core/Expression
+    (-static [_]
+      false)
+    (-attach-cache [_ context]
+      (as-op type pred (core/-attach-cache operand context)))
+    (-eval [_ context resource scope]
+      (let [value (core/-eval operand context resource scope)]
+        (when (pred value)
+          value)))
+    (-form [_]
+      `(~'as ~type ~(core/-form operand)))))
+
+
 (defmethod core/compile* :elm.compiler.type/as
   [context {:keys [operand] :as expression}]
   (when-some [operand (core/compile* context operand)]
     (let [[type pred] (matches-type-fn expression)]
-      (reify core/Expression
-        (-static [_]
-          false)
-        (-eval [_ context resource scope]
-          (let [value (core/-eval operand context resource scope)]
-            (when (pred value)
-              value)))
-        (-form [_]
-          `(~'as ~type ~(core/-form operand)))))))
+      (as-op type pred operand))))
 
 
 ;; TODO 22.2. CanConvert
diff --git a/modules/cql/src/blaze/elm/compiler_spec.clj b/modules/cql/src/blaze/elm/compiler_spec.clj
index fe1ce022d..bcf3bf183 100644
--- a/modules/cql/src/blaze/elm/compiler_spec.clj
+++ b/modules/cql/src/blaze/elm/compiler_spec.clj
@@ -3,6 +3,8 @@
     [blaze.elm.compiler :as c]
     [blaze.elm.compiler.core :as core]
     [blaze.elm.compiler.spec]
+    [blaze.elm.expression :as-alias expr]
+    [blaze.elm.expression.spec]
     [blaze.elm.spec]
     [blaze.fhir.spec-spec]
     [clojure.spec.alpha :as s]))
@@ -11,3 +13,8 @@
 (s/fdef c/compile
   :args (s/cat :context :elm/compile-context :expression :elm/expression)
   :ret core/expr?)
+
+
+(s/fdef c/attach-cache
+  :args (s/cat :context ::expr/attach-cache-context :expression core/expr?)
+  :ret core/expr?)
diff --git a/modules/cql/src/blaze/elm/expression.clj b/modules/cql/src/blaze/elm/expression.clj
index 5c769b643..912a980c2 100644
--- a/modules/cql/src/blaze/elm/expression.clj
+++ b/modules/cql/src/blaze/elm/expression.clj
@@ -1,5 +1,5 @@
 (ns blaze.elm.expression
-  (:refer-clojure :exclude [eval])
+  (:refer-clojure :exclude [eval hash])
   (:require
     [blaze.elm.compiler.core :as core]))
 
@@ -10,3 +10,9 @@
   Throws an Exception on errors."
   [context expression resource]
   (core/-eval expression context resource nil))
+
+
+(defn hash
+  "Hashes `expression`."
+  [expression]
+  (clojure.core/hash (core/-form expression)))
diff --git a/modules/cql/src/blaze/elm/expression/spec.clj b/modules/cql/src/blaze/elm/expression/spec.clj
index 0683e3afc..5571b33b4 100644
--- a/modules/cql/src/blaze/elm/expression/spec.clj
+++ b/modules/cql/src/blaze/elm/expression/spec.clj
@@ -5,13 +5,19 @@
     [blaze.elm.expression :as-alias expr]
     [blaze.elm.spec]
     [clojure.spec.alpha :as s]
-    [java-time.api :as time]))
+    [java-time.api :as time])
+  (:import
+    [com.github.benmanes.caffeine.cache AsyncCache]))
 
 
 (s/def ::now
   time/offset-date-time?)
 
 
+(s/def ::expr/cache
+  #(instance? AsyncCache %))
+
+
 (s/def ::parameters
   (s/map-of :elm/name ::c/expression))
 
@@ -19,3 +25,7 @@
 (s/def ::expr/context
   (s/keys :req-un [:blaze.db/db ::now]
           :opt-un [::c/expression-defs ::parameters]))
+
+
+(s/def ::expr/attach-cache-context
+  (s/merge ::expr/context (s/keys :req [::expr/cache])))
diff --git a/modules/cql/src/blaze/elm/expression_spec.clj b/modules/cql/src/blaze/elm/expression_spec.clj
index 307666857..4b50396bb 100644
--- a/modules/cql/src/blaze/elm/expression_spec.clj
+++ b/modules/cql/src/blaze/elm/expression_spec.clj
@@ -15,3 +15,8 @@
   :args (s/cat :context ::expr/context
                :expression ::c/expression
                :resource (s/nilable ed/resource?)))
+
+
+(s/fdef expr/hash
+  :args (s/cat :expression ::c/expression)
+  :ret int?)
diff --git a/modules/cql/test/blaze/elm/compiler/conditional_operators_test.clj b/modules/cql/test/blaze/elm/compiler/conditional_operators_test.clj
index f4ce27b4c..6846e1f14 100644
--- a/modules/cql/test/blaze/elm/compiler/conditional_operators_test.clj
+++ b/modules/cql/test/blaze/elm/compiler/conditional_operators_test.clj
@@ -94,20 +94,20 @@
         (let [expr (tu/dynamic-compile
                      {:type "Case"
                       :caseItem
-                      [{:when #elm/parameter-ref "true"
-                        :then #elm/integer "1"}]
-                      :else #elm/integer "2"})]
-          (has-form expr '(case (param-ref "true") 1 2))))
+                      [{:when #elm/parameter-ref "x"
+                        :then #elm/parameter-ref "y"}]
+                      :else #elm/parameter-ref "z"})]
+          (has-form expr '(case (param-ref "x") (param-ref "y") (param-ref "z")))))
 
       (testing "comparand-based"
         (let [expr (tu/dynamic-compile
                      {:type "Case"
                       :comparand #elm/parameter-ref "a"
                       :caseItem
-                      [{:when #elm/parameter-ref "b"
-                        :then #elm/integer "1"}]
-                      :else #elm/integer "2"})]
-          (has-form expr '(case (param-ref "a") (param-ref "b") 1 2))))))
+                      [{:when #elm/parameter-ref "x"
+                        :then #elm/parameter-ref "y"}]
+                      :else #elm/parameter-ref "z"})]
+          (has-form expr '(case (param-ref "a") (param-ref "x") (param-ref "y") (param-ref "z")))))))
 
   (testing "expression is dynamic"
     (testing "multi-conditional"
@@ -149,4 +149,16 @@
   (testing "expression is dynamic"
     (is (false? (core/-static (tu/dynamic-compile #elm/if [#elm/parameter-ref "x"
                                                            #elm/parameter-ref "y"
-                                                           #elm/parameter-ref "z"]))))))
+                                                           #elm/parameter-ref "z"])))))
+
+  (testing "form"
+    (let [expr (c/compile {} #elm/if [#elm/boolean "true" #elm/integer "1" #elm/integer "2"])]
+      (has-form expr 1))
+
+    (let [expr (c/compile {} #elm/if [#elm/boolean "false" #elm/integer "1" #elm/integer "2"])]
+      (has-form expr 2))
+
+    (let [expr (tu/dynamic-compile #elm/if [#elm/parameter-ref "x"
+                                            #elm/parameter-ref "y"
+                                            #elm/parameter-ref "z"])]
+      (has-form expr '(if (param-ref "x") (param-ref "y") (param-ref "z"))))))
diff --git a/modules/cql/test/blaze/elm/compiler/expr_cache_spec.clj b/modules/cql/test/blaze/elm/compiler/expr_cache_spec.clj
new file mode 100644
index 000000000..58c529db8
--- /dev/null
+++ b/modules/cql/test/blaze/elm/compiler/expr_cache_spec.clj
@@ -0,0 +1,12 @@
+(ns blaze.elm.compiler.expr-cache-spec
+  (:require
+    [blaze.db.tx-log.spec]
+    [blaze.elm.compiler.expr-cache :as ec]
+    [blaze.fhir.spec.spec]
+    [clojure.spec.alpha :as s]))
+
+
+(s/fdef ec/cache
+  :args (s/cat :t :blaze.db/t
+               :resource-ids (s/coll-of :blaze.resource/id :kind vector?))
+  :ret ec/cache?)
diff --git a/modules/cql/test/blaze/elm/compiler/external_data_test.clj b/modules/cql/test/blaze/elm/compiler/external_data_test.clj
index 1c96b7e4b..13785a0ab 100644
--- a/modules/cql/test/blaze/elm/compiler/external_data_test.clj
+++ b/modules/cql/test/blaze/elm/compiler/external_data_test.clj
@@ -16,7 +16,6 @@
     [blaze.elm.compiler.test-util :as tu :refer [has-form]]
     [blaze.elm.expression :as expr]
     [blaze.elm.expression-spec]
-    [blaze.elm.expression.cache :as-alias expr-cache]
     [blaze.fhir.spec :as fhir-spec]
     [blaze.fhir.spec.type]
     [blaze.module.test-util :refer [with-system]]
@@ -401,9 +400,7 @@
                          define InInitialPopulation:
                            [\"name-133756\" -> Observation]
                          ")
-              compile-context {::expr-cache/enabled? false}
-              {:keys [expression-defs]} (library/compile-library
-                                          node library compile-context)
+              {:keys [expression-defs]} (library/compile-library node library {})
               db (d/db node)
               patient (resource db "Patient" "0")
               eval-context (assoc (eval-context db) :expression-defs expression-defs)
@@ -448,9 +445,7 @@
                          define InInitialPopulation:
                            [\"name-133730\" -> Observation: Code 'code-133657' from sys]
                          ")
-              compile-context {::expr-cache/enabled? false}
-              {:keys [expression-defs]} (library/compile-library
-                                          node library compile-context)
+              {:keys [expression-defs]} (library/compile-library node library {})
               db (d/db node)
               patient (resource db "Patient" "0")
               eval-context (assoc (eval-context db) :expression-defs expression-defs)
diff --git a/modules/cql/test/blaze/elm/compiler/library_test.clj b/modules/cql/test/blaze/elm/compiler/library_test.clj
index 9186742c9..cec899581 100644
--- a/modules/cql/test/blaze/elm/compiler/library_test.clj
+++ b/modules/cql/test/blaze/elm/compiler/library_test.clj
@@ -20,6 +20,9 @@
 (test/use-fixtures :each tu/fixture)
 
 
+(def default-opts {})
+
+
 ;; 5.1. Library
 ;;
 ;; 1. The identifier element defines a unique identifier for this library, and
@@ -60,13 +63,13 @@
   (testing "empty library"
     (let [library (t/translate "library Test")]
       (with-system [{:blaze.db/keys [node]} mem-node-config]
-        (given (library/compile-library node library {})
+        (given (library/compile-library node library default-opts)
           :expression-defs := {}))))
 
   (testing "one static expression"
     (let [library (t/translate "library Test define Foo: true")]
       (with-system [{:blaze.db/keys [node]} mem-node-config]
-        (given (library/compile-library node library {})
+        (given (library/compile-library node library default-opts)
           [:expression-defs "Foo" :context] := "Patient"
           [:expression-defs "Foo" :expression] := true))))
 
@@ -76,7 +79,7 @@
       context Patient
       define Gender: Patient.gender")]
       (with-system [{:blaze.db/keys [node]} mem-node-config]
-        (given (library/compile-library node library {})
+        (given (library/compile-library node library default-opts)
           [:expression-defs "Gender" :context] := "Patient"
           [:expression-defs "Gender" :expression c/form] := '(:gender (expr-ref "Patient"))))))
 
@@ -87,7 +90,7 @@
       define function Gender(P Patient): P.gender
       define InInitialPopulation: Gender(Patient)")]
       (with-system [{:blaze.db/keys [node]} mem-node-config]
-        (given (library/compile-library node library {})
+        (given (library/compile-library node library default-opts)
           [:expression-defs "InInitialPopulation" :context] := "Patient"
           [:expression-defs "InInitialPopulation" :resultTypeName] := "{http://hl7.org/fhir}AdministrativeGender"
           [:expression-defs "InInitialPopulation" :expression c/form] := '(call "Gender" (expr-ref "Patient"))
@@ -103,7 +106,7 @@
       define function Inc2(i System.Integer): Inc(i) + 1
       define InInitialPopulation: Inc2(1)")]
       (with-system [{:blaze.db/keys [node]} mem-node-config]
-        (given (library/compile-library node library {})
+        (given (library/compile-library node library default-opts)
           [:expression-defs "InInitialPopulation" :context] := "Patient"
           [:expression-defs "InInitialPopulation" :expression c/form] := '(call "Inc2" 1)))))
 
@@ -112,7 +115,7 @@
       (let [library (t/translate "library Test
           define function Error(): singleton from {1, 2}")]
         (with-system [{:blaze.db/keys [node]} mem-node-config]
-          (given (library/compile-library node library {})
+          (given (library/compile-library node library default-opts)
             ::anom/category := ::anom/conflict
             ::anom/message := "More than one element in `SingletonFrom` expression."))))
 
@@ -120,7 +123,7 @@
       (let [library (t/translate "library Test
         define Error: singleton from {1, 2}")]
         (with-system [{:blaze.db/keys [node]} mem-node-config]
-          (given (library/compile-library node library {})
+          (given (library/compile-library node library default-opts)
             ::anom/category := ::anom/conflict
             ::anom/message := "More than one element in `SingletonFrom` expression.")))))
 
@@ -128,7 +131,7 @@
     (let [library (t/translate "library Test
     parameter \"Measurement Period\" Interval<Date> default Interval[@2020-01-01, @2020-12-31]")]
       (with-system [{:blaze.db/keys [node]} mem-node-config]
-        (given (library/compile-library node library {})
+        (given (library/compile-library node library default-opts)
           [:parameter-default-values "Measurement Period" :start] := #system/date"2020-01-01"
           [:parameter-default-values "Measurement Period" :end] := #system/date"2020-12-31"))))
 
@@ -136,6 +139,6 @@
     (let [library (t/translate "library Test
     parameter \"Measurement Start\" Integer default singleton from {1, 2}")]
       (with-system [{:blaze.db/keys [node]} mem-node-config]
-        (given (library/compile-library node library {})
+        (given (library/compile-library node library default-opts)
           ::anom/category := ::anom/conflict
           ::anom/message "More than one element in `SingletonFrom` expression.")))))
diff --git a/modules/cql/test/blaze/elm/compiler/list_operators_test.clj b/modules/cql/test/blaze/elm/compiler/list_operators_test.clj
index 39a530015..59ae88ed2 100644
--- a/modules/cql/test/blaze/elm/compiler/list_operators_test.clj
+++ b/modules/cql/test/blaze/elm/compiler/list_operators_test.clj
@@ -5,14 +5,18 @@
   https://cql.hl7.org/04-logicalspecification.html."
   (:require
     [blaze.anomaly-spec]
+    [blaze.db.api :as d]
+    [blaze.db.api-stub :refer [mem-node-config with-system-data]]
     [blaze.elm.compiler :as c]
     [blaze.elm.compiler-spec]
     [blaze.elm.compiler.core :as core]
     [blaze.elm.compiler.core-spec]
+    [blaze.elm.compiler.expr-cache-spec]
+    [blaze.elm.compiler.external-data :as ed]
     [blaze.elm.compiler.list-operators]
     [blaze.elm.compiler.test-util :as tu :refer [has-form]]
+    [blaze.elm.expression :as expr]
     [blaze.elm.expression-spec]
-    [blaze.elm.expression.cache :as-alias expr-cache]
     [blaze.elm.literal :as elm]
     [blaze.elm.literal-spec]
     [blaze.elm.quantity :as quantity]
@@ -20,9 +24,13 @@
     [clojure.spec.alpha :as s]
     [clojure.spec.test.alpha :as st]
     [clojure.test :as test :refer [are deftest is testing]]
-    [clojure.test.check.properties :as prop]))
+    [clojure.test.check.properties :as prop])
+  (:import
+    [com.github.benmanes.caffeine.cache Caffeine]
+    [java.time OffsetDateTime]))
 
 
+(set! *warn-on-reflection* true)
 (st/instrument)
 (tu/instrument-compile)
 
@@ -153,7 +161,7 @@
 
 ;; 20.8. Exists
 ;;
-;; The Exists operator returns true if the list contains any elements.
+;; The Exists operator returns true if the list contains any non-null elements.
 ;;
 ;; If the argument is null, the result is false.
 (deftest compile-exists-test
@@ -175,7 +183,82 @@
 
       {:type "Null"} false)
 
-    (tu/testing-unary-form elm/exists)))
+    (testing "with caching expressions"
+      (with-system-data [{:blaze.db/keys [node]} mem-node-config]
+        [[[:put {:fhir/type :fhir/Patient :id "0"}]]]
+
+        (let [db (d/db node)
+              patient (ed/mk-resource db (d/resource-handle db "Patient" "0"))
+              elm #elm/exists #elm/retrieve{:type "Observation"}
+              compile-context
+              {:node node
+               :eval-context "Patient"
+               :library {}}
+              expr (c/compile compile-context elm)
+              attach-cache-context
+              {:db db
+               ::expr/cache (.buildAsync (Caffeine/newBuilder))
+               :now (OffsetDateTime/now)}
+              eval-context
+              {:db db
+               :now (OffsetDateTime/now)}]
+
+          (testing "has no Observation at the beginning"
+            (let [expr (c/attach-cache attach-cache-context expr)]
+              (is (false? (expr/eval eval-context expr patient)))))
+
+          (Thread/sleep 100)
+
+          (testing "has still no Observation after the Bloom filter is filled"
+            (let [expr (c/attach-cache attach-cache-context expr)]
+              (is (false? (expr/eval eval-context expr patient)))))
+
+          (let [tx-op [:put {:fhir/type :fhir/Observation :id "0"
+                             :subject #fhir/Reference{:reference "Patient/0"}}]
+                db-after @(d/transact node [tx-op])]
+
+            (testing "has an Observation after transaction"
+              (let [expr (c/attach-cache attach-cache-context expr)
+                    patient (ed/mk-resource db-after (d/resource-handle db "Patient" "0"))]
+                (is (true? (expr/eval (assoc eval-context :db db-after) expr patient)))))
+
+            (testing "has still no Observation at the old database"
+              (let [expr (c/attach-cache attach-cache-context expr)]
+                (is (false? (expr/eval eval-context expr patient)))))))))
+
+    (testing "without caching expressions"
+      (with-system-data [{:blaze.db/keys [node]} mem-node-config]
+        [[[:put {:fhir/type :fhir/Patient :id "0"}]]]
+
+        (let [db (d/db node)
+              patient (ed/mk-resource db (d/resource-handle db "Patient" "0"))
+              elm #elm/exists #elm/retrieve{:type "Observation"}
+              compile-context
+              {:node node
+               :eval-context "Patient"
+               :library {}}
+              expr (c/compile compile-context elm)
+              eval-context
+              {:db db
+               :now (OffsetDateTime/now)}]
+
+          (testing "has no Observation at the beginning"
+            (is (false? (expr/eval eval-context expr patient))))
+
+          (let [tx-op [:put {:fhir/type :fhir/Observation :id "0"
+                             :subject #fhir/Reference{:reference "Patient/0"}}]
+                db-after @(d/transact node [tx-op])]
+
+            (testing "has an Observation after transaction"
+              (let [patient (ed/mk-resource db-after (d/resource-handle db "Patient" "0"))]
+                (is (true? (expr/eval (assoc eval-context :db db-after) expr patient)))))
+
+            (testing "has still no Observation at the old database"
+              (is (false? (expr/eval eval-context expr patient)))))))))
+
+  (tu/testing-unary-dynamic elm/exists)
+
+  (tu/testing-unary-form elm/exists))
 
 
 ;; 20.9. Filter
diff --git a/modules/cql/test/blaze/elm/compiler/queries_test.clj b/modules/cql/test/blaze/elm/compiler/queries_test.clj
index 57bf10167..4027d6dfb 100644
--- a/modules/cql/test/blaze/elm/compiler/queries_test.clj
+++ b/modules/cql/test/blaze/elm/compiler/queries_test.clj
@@ -48,34 +48,48 @@
   (testing "Non-retrieve queries"
     (testing "Sort"
       (testing "ByDirection"
-        (are [query res] (= res (core/-eval (c/compile {} query) {} nil nil))
-          {:type "Query"
-           :source
-           [{:alias "S"
-             :expression #elm/list [#elm/integer "2" #elm/integer "1" #elm/integer "1"]}]
-           :sort {:by [{:type "ByDirection" :direction "asc"}]}}
-          [1 2]))
+        (let [elm {:type "Query"
+                   :source
+                   [{:alias "S"
+                     :expression #elm/list [#elm/integer "2" #elm/integer "1" #elm/integer "1"]}]
+                   :sort {:by [{:type "ByDirection" :direction "asc"}]}}
+              expr (c/compile {} elm)]
+
+          (testing "eval"
+            (is (= [1 2] (core/-eval expr {} nil nil))))
+
+          (testing "form"
+            (has-form expr '(sorted-vector-query distinct [2 1 1] asc)))))
 
       (testing "ByExpression"
-        (are [query res] (= res (core/-eval (c/compile {} query) {} nil nil))
-          {:type "Query"
-           :source
-           [{:alias "S"
-             :expression
-             #elm/list
-                     [#elm/quantity [2 "m"]
-                      #elm/quantity [1 "m"]
-                      #elm/quantity [1 "m"]]}]
-           :sort
-           {:by
-            [{:type "ByExpression"
-              :direction "asc"
-              :expression
-              {:type "Property"
-               :path "value"
-               :scope "S"
-               :resultTypeName "{urn:hl7-org:elm-types:r1}decimal"}}]}}
-          [(quantity/quantity 1 "m") (quantity/quantity 2 "m")])
+        (let [elm {:type "Query"
+                   :source
+                   [{:alias "S"
+                     :expression
+                     #elm/list
+                             [#elm/quantity [2 "m"]
+                              #elm/quantity [1 "m"]
+                              #elm/quantity [1 "m"]]}]
+                   :sort
+                   {:by
+                    [{:type "ByExpression"
+                      :direction "asc"
+                      :expression
+                      {:type "Property"
+                       :path "value"
+                       :scope "S"
+                       :resultTypeName "{urn:hl7-org:elm-types:r1}decimal"}}]}}
+              expr (c/compile {} elm)]
+
+          (testing "eval"
+            (is (= [(quantity/quantity 1 "m") (quantity/quantity 2 "m")] (core/-eval expr {} nil nil))))
+
+          (testing "form"
+            (has-form expr '(sorted-vector-query distinct
+                                                 [(quantity 2 "m")
+                                                  (quantity 1 "m")
+                                                  (quantity 1 "m")]
+                                                 [asc (:value S)]))))
 
         (testing "with IdentifierRef"
           (are [query res] (= res (core/-eval (c/compile {} query) {} nil nil))
diff --git a/modules/cql/test/blaze/elm/compiler/test_util.clj b/modules/cql/test/blaze/elm/compiler/test_util.clj
index 6e39cbc1f..156e36abc 100644
--- a/modules/cql/test/blaze/elm/compiler/test_util.clj
+++ b/modules/cql/test/blaze/elm/compiler/test_util.clj
@@ -48,7 +48,8 @@
 
 
 (def dynamic-compile-ctx
-  {:library
+  {:eval-context "Patient"
+   :library
    {:parameters
     {:def
      [{:name "true"}
diff --git a/modules/db-protocols/src/blaze/db/impl/protocols.clj b/modules/db-protocols/src/blaze/db/impl/protocols.clj
index 982e57ce9..9a1ef5ca5 100644
--- a/modules/db-protocols/src/blaze/db/impl/protocols.clj
+++ b/modules/db-protocols/src/blaze/db/impl/protocols.clj
@@ -24,6 +24,8 @@
     [db compartment tid]
     [db compartment tid start-id])
 
+  (-patient-compartment-last-change-t [db patient-id])
+
   (-count-query [db query]
     "Returns a CompletableFuture that will complete with the count of the
     matching resource handles.")
@@ -109,4 +111,4 @@
   (-list-by-type [_ type])
   (-list-by-target [_ target])
   (-linked-compartments [_ resource])
-  (-compartment-resources [_ type]))
+  (-compartment-resources [_ compartment-type] [_ compartment-type type]))
diff --git a/modules/db-stub/src/blaze/db/api_stub.clj b/modules/db-stub/src/blaze/db/api_stub.clj
index 9c4123355..561de85f2 100644
--- a/modules/db-stub/src/blaze/db/api_stub.clj
+++ b/modules/db-stub/src/blaze/db/api_stub.clj
@@ -29,6 +29,7 @@
       :kv-store (ig/ref :blaze.db/index-kv-store)
       :resource-indexer (ig/ref :blaze.db.node/resource-indexer)
       :search-param-registry (ig/ref :blaze.db/search-param-registry)
+      :scheduler (ig/ref :blaze/scheduler)
       :poll-timeout (time/millis 10)}
      node-config)
 
@@ -57,6 +58,7 @@
      :resource-as-of-index nil
      :type-as-of-index nil
      :system-as-of-index nil
+     :patient-as-of-index nil
      :type-stats-index nil
      :system-stats-index nil}}
 
@@ -76,7 +78,9 @@
    :blaze.db.node.resource-indexer/executor {}
 
    :blaze.db/search-param-registry
-   {:structure-definition-repo structure-definition-repo}})
+   {:structure-definition-repo structure-definition-repo}
+
+   :blaze/scheduler {}})
 
 
 (def mem-node-config
diff --git a/modules/db/.clj-kondo/config.edn b/modules/db/.clj-kondo/config.edn
index 3d510f5ed..f57f4bffc 100644
--- a/modules/db/.clj-kondo/config.edn
+++ b/modules/db/.clj-kondo/config.edn
@@ -38,6 +38,7 @@
     blaze.db.impl.protocols p
     blaze.db.search-param-registry sr
     blaze.executors ex
+    blaze.scheduler sched
     buddy.auth auth
     cognitect.anomalies anom
     clojure.java.io io
diff --git a/modules/db/deps.edn b/modules/db/deps.edn
index 8023f0d6d..90e89975d 100644
--- a/modules/db/deps.edn
+++ b/modules/db/deps.edn
@@ -10,6 +10,9 @@
   blaze/byte-string
   {:local/root "../byte-string"}
 
+  blaze/cache-collector
+  {:local/root "../cache-collector"}
+
   blaze/coll
   {:local/root "../coll"}
 
@@ -34,6 +37,9 @@
   blaze/db-resource-store
   {:local/root "../db-resource-store"}
 
+  blaze/scheduler
+  {:local/root "../scheduler"}
+
   blaze/spec
   {:local/root "../spec"}
 
diff --git a/modules/db/src/blaze/db/api.clj b/modules/db/src/blaze/db/api.clj
index cc921e3bc..1d0138327 100644
--- a/modules/db/src/blaze/db/api.clj
+++ b/modules/db/src/blaze/db/api.clj
@@ -290,6 +290,13 @@
 
 
 
+;; ---- Patient-Compartment-Level Functions -----------------------------------
+
+(defn patient-compartment-last-change-t [db patient-id]
+  (p/-patient-compartment-last-change-t db (codec/id-byte-string patient-id)))
+
+
+
 ;; ---- Common Query Functions ------------------------------------------------
 
 (defn count-query
diff --git a/modules/db/src/blaze/db/cache_collector/spec.clj b/modules/db/src/blaze/db/cache_collector/spec.clj
deleted file mode 100644
index 1f515be65..000000000
--- a/modules/db/src/blaze/db/cache_collector/spec.clj
+++ /dev/null
@@ -1,8 +0,0 @@
-(ns blaze.db.cache-collector.spec
-  (:require
-    [blaze.db.cache-collector.protocols :as p]
-    [clojure.spec.alpha :as s]))
-
-
-(s/def :blaze.db.cache-collector/caches
-  (s/map-of string? (s/nilable #(satisfies? p/StatsCache %))))
diff --git a/modules/db/src/blaze/db/impl/batch_db.clj b/modules/db/src/blaze/db/impl/batch_db.clj
index 89a087c8f..ebe707bfe 100644
--- a/modules/db/src/blaze/db/impl/batch_db.clj
+++ b/modules/db/src/blaze/db/impl/batch_db.clj
@@ -9,6 +9,7 @@
     [blaze.db.impl.codec :as codec]
     [blaze.db.impl.index :as index]
     [blaze.db.impl.index.compartment.resource :as cr]
+    [blaze.db.impl.index.patient-as-of :as pao]
     [blaze.db.impl.index.resource-as-of :as rao]
     [blaze.db.impl.index.resource-handle :as rh]
     [blaze.db.impl.index.search-param-value-resource :as sp-vr]
@@ -37,7 +38,7 @@
     (:total (type-stats/get! iter tid t) 0)))
 
 
-(defrecord BatchDb [node basis-t context]
+(defrecord BatchDb [node basis-t t context]
   p/Db
   (-node [_]
     node)
@@ -45,6 +46,9 @@
   (-basis-t [_]
     basis-t)
 
+  (-as-of-t [_]
+    (when (not= basis-t t) t))
+
 
 
   ;; ---- Instance-Level Functions --------------------------------------------
@@ -92,6 +96,13 @@
 
 
 
+  ;; ---- Patient-Compartment-Level Functions ---------------------------------
+
+  (-patient-compartment-last-change-t [_ patient-id]
+    (pao/last-change-t (:paoi context) patient-id t))
+
+
+
   ;; ---- Common Query Functions ----------------------------------------------
 
   (-count-query [_ query]
@@ -236,8 +247,9 @@
 
   AutoCloseable
   (close [_]
-    (let [{:keys [snapshot raoi svri rsvi cri csvri]} context]
+    (let [{:keys [snapshot raoi paoi svri rsvi cri csvri]} context]
       (.close ^AutoCloseable raoi)
+      (.close ^AutoCloseable paoi)
       (.close ^AutoCloseable svri)
       (.close ^AutoCloseable rsvi)
       (.close ^AutoCloseable cri)
@@ -321,9 +333,11 @@
     (->BatchDb
       node
       basis-t
+      t
       (let [raoi (kv/new-iterator snapshot :resource-as-of-index)]
         {:snapshot snapshot
          :raoi raoi
+         :paoi (kv/new-iterator snapshot :patient-as-of-index)
          :resource-handle (rao/resource-handle raoi t)
          :svri (kv/new-iterator snapshot :search-param-value-index)
          :rsvi (kv/new-iterator snapshot :resource-value-index)
diff --git a/modules/db/src/blaze/db/impl/db.clj b/modules/db/src/blaze/db/impl/db.clj
index b2a30c0eb..3201a18bc 100644
--- a/modules/db/src/blaze/db/impl/db.clj
+++ b/modules/db/src/blaze/db/impl/db.clj
@@ -3,6 +3,7 @@
   (:require
     [blaze.async.comp :as ac]
     [blaze.db.impl.batch-db :as batch-db]
+    [blaze.db.impl.index.patient-as-of :as pao]
     [blaze.db.impl.index.resource-as-of :as rao]
     [blaze.db.impl.macros :refer [with-open-coll]]
     [blaze.db.impl.protocols :as p]
@@ -85,6 +86,15 @@
 
 
 
+  ;; ---- Patient-Compartment-Level Functions ---------------------------------
+
+  (-patient-compartment-last-change-t [_ patient-id]
+    (with-open [snapshot (kv/new-snapshot kv-store)
+                paoi (kv/new-iterator snapshot :patient-as-of-index)]
+      (pao/last-change-t paoi patient-id t)))
+
+
+
   ;; ---- Common Query Functions ----------------------------------------------
 
   (-count-query [_ query]
diff --git a/modules/db/src/blaze/db/impl/index/patient_as_of.clj b/modules/db/src/blaze/db/impl/index/patient_as_of.clj
new file mode 100644
index 000000000..b249b0109
--- /dev/null
+++ b/modules/db/src/blaze/db/impl/index/patient_as_of.clj
@@ -0,0 +1,87 @@
+(ns blaze.db.impl.index.patient-as-of
+  "Functions for accessing the PatientAsOf index."
+  (:require
+    [blaze.byte-buffer :as bb]
+    [blaze.byte-string :as bs]
+    [blaze.db.impl.codec :as codec]
+    [blaze.db.impl.index.rts-as-of :as rts]
+    [blaze.db.kv :as kv])
+  (:import
+    [java.nio.charset StandardCharsets]))
+
+
+(set! *warn-on-reflection* true)
+(set! *unchecked-math* :warn-on-boxed)
+
+
+(def ^:private ^:const ^long t-tid-size
+  (+ codec/t-size codec/tid-size))
+
+
+(defn- encode-key
+  "Encodes the key of the PatientAsOf index from `patient-id`, `t`, `tid` and
+  `id`."
+  [patient-id t tid id]
+  (-> (bb/allocate (-> (unchecked-add-int (bs/size patient-id) (bs/size id))
+                       (unchecked-add-int t-tid-size)))
+      (bb/put-byte-string! patient-id)
+      (bb/put-long! (codec/descending-long ^long t))
+      (bb/put-int! tid)
+      (bb/put-byte-string! id)
+      bb/array))
+
+
+(defn index-entry [patient-id tid id t hash num-changes op]
+  [:patient-as-of-index (encode-key patient-id t tid id)
+   (rts/encode-value hash num-changes op)])
+
+
+(defn- encode-patient-id-t [patient-id t]
+  (-> (bb/allocate (unchecked-add-int (bs/size patient-id) codec/t-size))
+      (bb/put-byte-string! patient-id)
+      (bb/put-long! (codec/descending-long ^long t))
+      bb/array))
+
+
+(defn last-change-t
+  "Returns the `t` of last change of any resource in the patient compartment not
+  newer than `t`."
+  [paoi patient-id t]
+  (kv/seek! paoi (encode-patient-id-t patient-id t))
+  (when (kv/valid? paoi)
+    (-> (bb/get-long! (bb/wrap (kv/key paoi)) (bs/size patient-id))
+        (codec/descending-long))))
+
+
+(def ^:private state-key
+  (.getBytes "patient-as-of-state" StandardCharsets/ISO_8859_1))
+
+
+(defn- encode-state [{:keys [type t]}]
+  (if (identical? :current type)
+    (byte-array [0])
+    (-> (bb/allocate (inc Long/BYTES))
+        (bb/put-byte! 1)
+        (bb/put-long! t)
+        bb/array)))
+
+
+(defn decode-state [bytes]
+  (let [buf (bb/wrap bytes)]
+    (if (zero? (bb/get-byte! buf))
+      {:type :current}
+      {:type :building
+       :t (bb/get-long! buf)})))
+
+
+(defn state
+  "Returns the state of the PatientAsOf index.
+
+  The state is on of :current or last-t."
+  [kv-store]
+  (or (some-> (kv/get kv-store state-key) decode-state)
+      {:type :building :t 0}))
+
+
+(defn state-index-entry [state]
+  [state-key (encode-state state)])
diff --git a/modules/db/src/blaze/db/node.clj b/modules/db/src/blaze/db/node.clj
index 8bcc308bb..110fa6d04 100644
--- a/modules/db/src/blaze/db/node.clj
+++ b/modules/db/src/blaze/db/node.clj
@@ -6,6 +6,7 @@
     [blaze.db.impl.batch-db :as batch-db]
     [blaze.db.impl.codec :as codec]
     [blaze.db.impl.db :as db]
+    [blaze.db.impl.index.patient-as-of :as pao]
     [blaze.db.impl.index.resource-handle :as rh]
     [blaze.db.impl.index.t-by-instant :as t-by-instant]
     [blaze.db.impl.index.tx-error :as tx-error]
@@ -15,6 +16,7 @@
     [blaze.db.impl.search-param.all :as search-param-all]
     [blaze.db.impl.search-param.chained :as spc]
     [blaze.db.kv :as kv]
+    [blaze.db.node.patient-as-of-index :as node-pao]
     [blaze.db.node.protocols :as np]
     [blaze.db.node.resource-indexer :as resource-indexer]
     [blaze.db.node.resource-indexer.spec]
@@ -31,6 +33,7 @@
     [blaze.fhir.spec :as fhir-spec]
     [blaze.fhir.spec.type :as type]
     [blaze.module :refer [reg-collector]]
+    [blaze.scheduler :as sched]
     [blaze.spec]
     [blaze.util :refer [conj-vec]]
     [clojure.spec.alpha :as s]
@@ -167,9 +170,9 @@
     future))
 
 
-(defn- index-tx [db-before tx-data]
+(defn- index-tx [search-param-registry db-before tx-data]
   (with-open [_ (prom/timer duration-seconds "index-transactions")]
-    (tx-indexer/index-tx db-before tx-data)))
+    (tx-indexer/index-tx search-param-registry db-before tx-data)))
 
 
 (defn- advance-t! [state t]
@@ -222,13 +225,13 @@
   "This is the main transaction handling function.
 
   If indexes resources and transaction data and commits either success or error."
-  [{:keys [resource-indexer kv-store] :as node}
+  [{:keys [resource-indexer kv-store search-param-registry] :as node}
    {:keys [t instant tx-cmds] :as tx-data}]
   (log/trace "index transaction with t =" t "and" (count tx-cmds) "command(s)")
   (prom/observe! transaction-sizes (count tx-cmds))
   (let [timer (prom/timer duration-seconds "index-resources")
         future (resource-indexer/index-resources resource-indexer tx-data)
-        result (index-tx (np/-db node) tx-data)]
+        result (index-tx search-param-registry (np/-db node) tx-data)]
     (if (ba/anomaly? result)
       (commit-error! node t result)
       (do
@@ -242,7 +245,11 @@
     (tx-log/poll! queue poll-timeout)))
 
 
-(defn- poll-and-index! [node queue poll-timeout]
+(defn- poll-and-index!
+  "Polls `queue` once and indexes the resulting transaction data.
+
+  Waits up to `poll-timeout` for the transaction data to become available."
+  [node queue poll-timeout]
   (log/trace "poll transaction queue")
   (run! (partial index-tx-data! node) (poll-tx-queue! queue poll-timeout)))
 
@@ -482,7 +489,8 @@
      :blaze.db/kv-store
      ::resource-indexer
      :blaze.db/resource-store
-     :blaze.db/search-param-registry]
+     :blaze.db/search-param-registry
+     :blaze/scheduler]
     :opt-un
     [:blaze.db/enforce-referential-integrity]))
 
@@ -530,9 +538,43 @@
       (ac/completed-future (db/db node (:t @(.-state node)))))))
 
 
+(defn- index-patient-as-of-index!
+  [{:keys [kv-store] :as node} current-t {:keys [t] :as tx-data}]
+  (log/debug "Build PatientAsOf index with t =" t)
+  (when-ok [entries (node-pao/index-entries node tx-data)]
+    (store-tx-entries! kv-store entries))
+  (vreset! current-t t))
+
+
+(defn- poll-and-index-patient-as-of-index! [node queue current-t poll-timeout]
+  (run! (partial index-patient-as-of-index! node current-t) (poll-tx-queue! queue poll-timeout)))
+
+
+(defn build-patient-as-of-index
+  [{:keys [tx-log kv-store run? state poll-timeout] :as node}]
+  (let [{:keys [type t]} (pao/state kv-store)]
+    (when (identical? :building type)
+      (let [start-t (inc t)
+            end-t (:t @state)
+            current-t (volatile! start-t)]
+        (log/info "Building PatientAsOf index starting at t =" start-t)
+        (with-open [queue (tx-log/new-queue tx-log start-t)]
+          (while (and @run? (< @current-t end-t))
+            (try
+              (poll-and-index-patient-as-of-index! node queue current-t poll-timeout)
+              (catch Exception e
+                (log/error "Error while building the PatientAsOf index." e)))))
+        (if (>= @current-t end-t)
+          (do
+            (store-tx-entries! kv-store [(pao/state-index-entry {:type :current})])
+            (log/info "Finished building PatientAsOf index."))
+          (log/info "Partially build PatientAsOf index up to t =" @current-t
+                    "at a goal of t =" end-t "Will continue at next start."))))))
+
+
 (defmethod ig/init-key :blaze.db/node
   [_ {:keys [storage tx-log tx-cache indexer-executor kv-store resource-indexer
-             resource-store search-param-registry poll-timeout]
+             resource-store search-param-registry scheduler poll-timeout]
       :or {poll-timeout (time/seconds 1)}
       :as config}]
   (init-msg config)
@@ -543,6 +585,8 @@
                      (volatile! true)
                      poll-timeout
                      (ac/future))]
+    (when (= :building (:type (pao/state kv-store)))
+      (sched/submit scheduler #(build-patient-as-of-index node)))
     (execute node indexer-executor)
     node))
 
diff --git a/modules/db/src/blaze/db/node/patient_as_of_index.clj b/modules/db/src/blaze/db/node/patient_as_of_index.clj
new file mode 100644
index 000000000..2b2614fbb
--- /dev/null
+++ b/modules/db/src/blaze/db/node/patient_as_of_index.clj
@@ -0,0 +1,14 @@
+(ns blaze.db.node.patient-as-of-index
+  (:require
+    [blaze.anomaly :refer [when-ok]]
+    [blaze.db.impl.db :as db]
+    [blaze.db.impl.index.patient-as-of :as pao]
+    [blaze.db.node.tx-indexer :as tx-indexer]))
+
+
+(defn index-entries
+  {:arglists '([node tx-data])}
+  [{:keys [search-param-registry] :as node} {:keys [t] :as tx-data}]
+  (when-ok [entries (tx-indexer/index-tx search-param-registry (db/db node (dec t)) tx-data)]
+    (-> (filterv (comp #{:patient-as-of-index} first) entries)
+        (conj (pao/state-index-entry {:type :building :t t})))))
diff --git a/modules/db/src/blaze/db/node/tx_indexer.clj b/modules/db/src/blaze/db/node/tx_indexer.clj
index c06510004..7c18d30f7 100644
--- a/modules/db/src/blaze/db/node/tx_indexer.clj
+++ b/modules/db/src/blaze/db/node/tx_indexer.clj
@@ -6,7 +6,7 @@
 
 
 (defn index-tx
-  [db-before {:keys [t tx-cmds]}]
+  [search-param-registry db-before {:keys [t tx-cmds]}]
   (log/trace "verify transaction commands with t =" t
              "based on db with t =" (d/basis-t db-before))
-  (verify/verify-tx-cmds db-before t tx-cmds))
+  (verify/verify-tx-cmds search-param-registry db-before t tx-cmds))
diff --git a/modules/db/src/blaze/db/node/tx_indexer/verify.clj b/modules/db/src/blaze/db/node/tx_indexer/verify.clj
index b3d72994a..c3d2e7fc9 100644
--- a/modules/db/src/blaze/db/node/tx_indexer/verify.clj
+++ b/modules/db/src/blaze/db/node/tx_indexer/verify.clj
@@ -3,11 +3,13 @@
     [blaze.anomaly :as ba :refer [throw-anom]]
     [blaze.db.api :as d]
     [blaze.db.impl.codec :as codec]
+    [blaze.db.impl.index.patient-as-of :as pao]
     [blaze.db.impl.index.resource-handle :as rh]
     [blaze.db.impl.index.rts-as-of :as rts]
     [blaze.db.impl.index.system-stats :as system-stats]
     [blaze.db.impl.index.type-stats :as type-stats]
     [blaze.db.kv.spec]
+    [blaze.db.search-param-registry :as sr]
     [blaze.fhir.hash :as hash]
     [blaze.util :as u]
     [clojure.string :as str]
@@ -115,8 +117,8 @@
   statistics of the transaction outcome.
 
   Throws an anomaly on conflicts."
-  {:arglists '([db-before t res cmd])}
-  (fn [_db-before _t _res {:keys [op]}] op))
+  {:arglists '([search-param-registry db-before t res cmd])}
+  (fn [_search-param-registry _db-before _t _res {:keys [op]}] op))
 
 
 (defn- verify-tx-cmd-create-msg [type id]
@@ -132,20 +134,27 @@
     (throw-anom (ba/conflict (id-collision-msg type id)))))
 
 
-(defn- index-entries [tid id t hash num-changes op]
-  (rts/index-entries tid (codec/id-byte-string id) t hash num-changes op))
+(defn- index-entries [tid id t hash num-changes op refs]
+  (let [id (codec/id-byte-string id)]
+    (into
+      (rts/index-entries tid id t hash num-changes op)
+      (keep (fn [[ref-type ref-id]]
+              (when (= "Patient" ref-type)
+                (pao/index-entry (codec/id-byte-string ref-id) tid id t hash
+                                 num-changes op))))
+      refs)))
 
 
 (def ^:private inc-0 (fnil inc 0))
 
 
 (defmethod verify-tx-cmd "create"
-  [db-before t res {:keys [type id hash]}]
+  [_search-param-registry db-before t res {:keys [type id hash refs]}]
   (log/trace (verify-tx-cmd-create-msg type id))
   (with-open [_ (prom/timer duration-seconds "verify-create")]
     (check-id-collision! db-before type id)
     (let [tid (codec/tid type)]
-      (-> (update res :entries into (index-entries tid id t hash 1 :create))
+      (-> (update res :entries into (index-entries tid id t hash 1 :create refs))
           (update :new-resources conj [type id])
           (update-in [:stats tid :num-changes] inc-0)
           (update-in [:stats tid :total] inc-0)))))
@@ -191,7 +200,8 @@
 
 
 (defmethod verify-tx-cmd "put"
-  [db-before t res {:keys [type id hash if-match if-none-match] :as tx-cmd}]
+  [_search-param-registry db-before t res
+   {:keys [type id hash if-match if-none-match refs] :as tx-cmd}]
   (log/trace (verify-tx-cmd-put-msg type id (u/to-seq if-match) if-none-match))
   (with-open [_ (prom/timer duration-seconds "verify-put")]
     (let [tid (codec/tid type)
@@ -213,7 +223,7 @@
 
         :else
         (cond->
-          (-> (update res :entries into (index-entries tid id t hash (inc num-changes) :put))
+          (-> (update res :entries into (index-entries tid id t hash (inc num-changes) :put refs))
               (update :new-resources conj [type id])
               (update-in [:stats tid :num-changes] inc-0))
           (or (nil? old-t) (identical? :delete op))
@@ -227,7 +237,7 @@
 
 
 (defmethod verify-tx-cmd "keep"
-  [db-before _ res {:keys [type id hash if-match] :as tx-cmd}]
+  [_search-param-registry db-before _ res {:keys [type id hash if-match] :as tx-cmd}]
   (log/trace (verify-tx-cmd-keep-msg type id (u/to-seq if-match)))
   (with-open [_ (prom/timer duration-seconds "verify-keep")]
     (let [if-match (u/to-seq if-match)
@@ -245,15 +255,24 @@
         res))))
 
 
+(defn- patient-refs [search-param-registry db type resource-handle]
+  (into
+    []
+    (comp (mapcat #(d/include db resource-handle % "Patient"))
+          (map (fn [{:keys [id]}] ["Patient" id])))
+    (sr/compartment-resources search-param-registry "Patient" type)))
+
+
 (defmethod verify-tx-cmd "delete"
-  [db-before t res {:keys [type id]}]
+  [search-param-registry db-before t res {:keys [type id]}]
   (log/trace "verify-tx-cmd :delete" (str type "/" id))
   (with-open [_ (prom/timer duration-seconds "verify-delete")]
     (let [tid (codec/tid type)
-          {:keys [num-changes op] :or {num-changes 0}}
-          (d/resource-handle db-before type id)]
+          {:keys [num-changes op] :or {num-changes 0} :as old-resource-handle}
+          (d/resource-handle db-before type id)
+          refs (some->> old-resource-handle (patient-refs search-param-registry db-before type))]
       (cond->
-        (-> (update res :entries into (index-entries tid id t hash/deleted-hash (inc num-changes) :delete))
+        (-> (update res :entries into (index-entries tid id t hash/deleted-hash (inc num-changes) :delete refs))
             (update :del-resources conj [type id])
             (update-in [:stats tid :num-changes] inc-0))
         (and op (not (identical? :delete op)))
@@ -261,13 +280,13 @@
 
 
 (defmethod verify-tx-cmd :default
-  [_db-before _t res _tx-cmd]
+  [_search-param-registry _db-before _t res _tx-cmd]
   res)
 
 
-(defn- verify-tx-cmds** [db-before t tx-cmds]
+(defn- verify-tx-cmds** [search-param-registry db-before t tx-cmds]
   (reduce
-    (partial verify-tx-cmd db-before t)
+    (partial verify-tx-cmd search-param-registry db-before t)
     {:entries []
      :new-resources #{}
      :del-resources #{}}
@@ -346,11 +365,11 @@
     cmds))
 
 
-(defn- verify-tx-cmds* [db-before t cmds]
+(defn- verify-tx-cmds* [search-param-registry db-before t cmds]
   (ba/try-anomaly
     (let [cmds (resolve-ids db-before cmds)]
       (detect-duplicate-commands! cmds)
-      (let [res (verify-tx-cmds** db-before t cmds)]
+      (let [res (verify-tx-cmds** search-param-registry db-before t cmds)]
         (check-referential-integrity! db-before res cmds)
         (post-process-res db-before t res)))))
 
@@ -360,7 +379,7 @@
   outcome if it is successful or an anomaly if it fails.
 
   The `t` is for the new transaction to commit."
-  [db-before t cmds]
+  [search-param-registry db-before t cmds]
   (with-open [_ (prom/timer duration-seconds "verify-tx-cmds")
               batch-db-before (d/new-batch-db db-before)]
-    (verify-tx-cmds* batch-db-before t cmds)))
+    (verify-tx-cmds* search-param-registry batch-db-before t cmds)))
diff --git a/modules/db/src/blaze/db/node/version.clj b/modules/db/src/blaze/db/node/version.clj
index 001532381..93c7d9d32 100644
--- a/modules/db/src/blaze/db/node/version.clj
+++ b/modules/db/src/blaze/db/node/version.clj
@@ -1,8 +1,7 @@
 (ns blaze.db.node.version
   (:refer-clojure :exclude [key])
-  (:require
-    [blaze.byte-buffer :as bb])
   (:import
+    [com.google.common.primitives Longs]
     [java.nio.charset StandardCharsets]))
 
 
@@ -14,10 +13,8 @@
 
 
 (defn encode-value [version]
-  (-> (bb/allocate Integer/BYTES)
-      (bb/put-int! version)
-      (bb/array)))
+  (Longs/toByteArray version))
 
 
 (defn decode-value [bytes]
-  (bb/get-int! (bb/wrap bytes)))
+  (Longs/fromByteArray bytes))
diff --git a/modules/db/src/blaze/db/resource_cache.clj b/modules/db/src/blaze/db/resource_cache.clj
index e9e2c1c6b..d6a580816 100644
--- a/modules/db/src/blaze/db/resource_cache.clj
+++ b/modules/db/src/blaze/db/resource_cache.clj
@@ -4,7 +4,7 @@
   Caffeine is used because it have better performance characteristics as a
   ConcurrentHashMap."
   (:require
-    [blaze.db.cache-collector.protocols :as ccp]
+    [blaze.cache-collector.protocols :as ccp]
     [blaze.db.resource-cache.spec]
     [blaze.db.resource-store :as rs]
     [blaze.db.resource-store.spec]
diff --git a/modules/db/src/blaze/db/search_param_registry.clj b/modules/db/src/blaze/db/search_param_registry.clj
index 9bdebac11..a976ede0b 100644
--- a/modules/db/src/blaze/db/search_param_registry.clj
+++ b/modules/db/src/blaze/db/search_param_registry.clj
@@ -47,16 +47,21 @@
 
 
 (defn compartment-resources
-  "Returns a seq of [type code] tuples of resources in compartment of `type`.
+  "Returns a seq of [type code] tuples of resources in compartment of
+  `compartment-type` or a list of codes if the optional `type` is given.
 
   Example:
-  * [\"Observation\" \"subject\"] and others for \"Patient\""
-  [search-param-registry type]
-  (p/-compartment-resources search-param-registry type))
+  * [\"Observation\" \"subject\"] and others for \"Patient\"
+  * [\"subject\"] and others for \"Patient\" and \"Observation\""
+  ([search-param-registry compartment-type]
+   (p/-compartment-resources search-param-registry compartment-type))
+  ([search-param-registry compartment-type type]
+   (p/-compartment-resources search-param-registry compartment-type type)))
 
 
 (deftype MemSearchParamRegistry [index target-index compartment-index
-                                 compartment-resource-index]
+                                 compartment-resource-index
+                                 compartment-resource-index-by-type]
   p/SearchParamRegistry
   (-get [_ code]
     (get-in index ["Resource" code]))
@@ -87,8 +92,11 @@
       #{}
       (compartment-index (name (fhir-spec/fhir-type resource)))))
 
-  (-compartment-resources [_ type]
-    (compartment-resource-index type [])))
+  (-compartment-resources [_ compartment-type]
+    (compartment-resource-index compartment-type []))
+
+  (-compartment-resources [_ compartment-type type]
+    (get-in compartment-resource-index-by-type [compartment-type type] [])))
 
 
 (def ^:private object-mapper
@@ -161,6 +169,15 @@
      resource-defs)})
 
 
+(defn- index-compartment-resources-by-type [{def-code :code resource-defs :resource}]
+  {def-code
+   (reduce
+     (fn [res {res-type :code param-codes :param}]
+       (cond-> res param-codes (assoc res-type param-codes)))
+     {}
+     resource-defs)})
+
+
 (def ^:private list-search-param
   {:type "special"
    :name "_list"})
@@ -258,7 +275,9 @@
         patient-compartment (read-classpath-json-resource "blaze/db/compartment/patient.json")]
     (when-ok [url-index (build-url-index entries)
               index (build-index url-index entries)]
-      (->MemSearchParamRegistry (add-special index)
-                                (build-target-index url-index entries)
-                                (index-compartment-def index patient-compartment)
-                                (index-compartment-resources patient-compartment)))))
+      (->MemSearchParamRegistry
+        (add-special index)
+        (build-target-index url-index entries)
+        (index-compartment-def index patient-compartment)
+        (index-compartment-resources patient-compartment)
+        (index-compartment-resources-by-type patient-compartment)))))
diff --git a/modules/db/src/blaze/db/search_param_registry_spec.clj b/modules/db/src/blaze/db/search_param_registry_spec.clj
index 859f19a2f..553a5cf8b 100644
--- a/modules/db/src/blaze/db/search_param_registry_spec.clj
+++ b/modules/db/src/blaze/db/search_param_registry_spec.clj
@@ -34,5 +34,6 @@
 
 (s/fdef sr/compartment-resources
   :args (s/cat :search-param-registry :blaze.db/search-param-registry
-               :type :fhir.resource/type)
+               :compartment-type :fhir.resource/type
+               :type (s/? :fhir.resource/type))
   :ret (s/coll-of (s/tuple :fhir.resource/type string?)))
diff --git a/modules/db/test-perf/blaze/db/api_test_perf.clj b/modules/db/test-perf/blaze/db/api_test_perf.clj
index 7bed864b9..dd0f4fd63 100644
--- a/modules/db/test-perf/blaze/db/api_test_perf.clj
+++ b/modules/db/test-perf/blaze/db/api_test_perf.clj
@@ -60,6 +60,7 @@
      :resource-as-of-index nil
      :type-as-of-index nil
      :system-as-of-index nil
+     :patient-as-of-index nil
      :type-stats-index nil
      :system-stats-index nil}}
 
diff --git a/modules/db/test/blaze/db/api_test.clj b/modules/db/test/blaze/db/api_test.clj
index ef95872ea..cca7cf046 100644
--- a/modules/db/test/blaze/db/api_test.clj
+++ b/modules/db/test/blaze/db/api_test.clj
@@ -4738,6 +4738,42 @@
           [0 :id] := "0")))))
 
 
+(deftest patient-compartment-last-change-t-test
+  (testing "non-existing patient"
+    (with-system [{:blaze.db/keys [node]} config]
+
+      (testing "just returns nil"
+        (is (nil? (d/patient-compartment-last-change-t (d/db node) "0"))))))
+
+  (testing "single patient"
+    (with-system-data [{:blaze.db/keys [node]} config]
+      [[[:put {:fhir/type :fhir/Patient :id "0"}]]]
+
+      (testing "has no resources in its compartment"
+        (is (nil? (d/patient-compartment-last-change-t (d/db node) "0"))))))
+
+
+  (testing "observation created in same transaction as patient"
+    (with-system-data [{:blaze.db/keys [node]} config]
+      [[[:put {:fhir/type :fhir/Patient :id "0"}]
+        [:put {:fhir/type :fhir/Observation :id "0"
+               :subject #fhir/Reference{:reference "Patient/0"}}]]]
+
+      (is (= 1 (d/patient-compartment-last-change-t (d/db node) "0")))))
+
+  (testing "observation created after the patient"
+    (with-system-data [{:blaze.db/keys [node]} config]
+      [[[:put {:fhir/type :fhir/Patient :id "0"}]]
+       [[:put {:fhir/type :fhir/Observation :id "0"
+               :subject #fhir/Reference{:reference "Patient/0"}}]]]
+
+      (testing "the last change comes from the second transaction"
+        (is (= 2 (d/patient-compartment-last-change-t (d/db node) "0"))))
+
+      (testing "at t=1 there was no change"
+        (is (nil? (d/patient-compartment-last-change-t (d/as-of (d/db node) 1) "0")))))))
+
+
 (defmethod ig/init-key ::defective-resource-store [_ {:keys [hashes-to-store]}]
   (let [store (atom {})]
     (reify
diff --git a/modules/db/test/blaze/db/impl/batch_db_spec.clj b/modules/db/test/blaze/db/impl/batch_db_spec.clj
index dfef7c8a6..08100df1c 100644
--- a/modules/db/test/blaze/db/impl/batch_db_spec.clj
+++ b/modules/db/test/blaze/db/impl/batch_db_spec.clj
@@ -3,6 +3,7 @@
     [blaze.byte-string-spec]
     [blaze.db.impl.batch-db :as batch-db]
     [blaze.db.impl.index.compartment.resource-spec]
+    [blaze.db.impl.index.patient-as-of-spec]
     [blaze.db.impl.index.resource-as-of-spec]
     [blaze.db.impl.index.system-as-of-spec]
     [blaze.db.impl.index.type-as-of-spec]
diff --git a/modules/db/test/blaze/db/impl/db_spec.clj b/modules/db/test/blaze/db/impl/db_spec.clj
index 1efc82cd5..a4e5577c3 100644
--- a/modules/db/test/blaze/db/impl/db_spec.clj
+++ b/modules/db/test/blaze/db/impl/db_spec.clj
@@ -5,6 +5,7 @@
     [blaze.db.impl.codec-spec]
     [blaze.db.impl.db :as db]
     [blaze.db.impl.index-spec]
+    [blaze.db.impl.index.patient-as-of-spec]
     [blaze.db.impl.index.system-stats-spec]
     [blaze.db.impl.index.type-stats-spec]
     [blaze.db.impl.search-param-spec]
diff --git a/modules/db/test/blaze/db/impl/index/patient_as_of_spec.clj b/modules/db/test/blaze/db/impl/index/patient_as_of_spec.clj
new file mode 100644
index 000000000..64c10ffe1
--- /dev/null
+++ b/modules/db/test/blaze/db/impl/index/patient_as_of_spec.clj
@@ -0,0 +1,26 @@
+(ns blaze.db.impl.index.patient-as-of-spec
+  (:require
+    [blaze.db.impl.codec-spec]
+    [blaze.db.impl.index.patient-as-of :as pao]
+    [blaze.db.kv-spec]
+    [blaze.db.tx-log.spec]
+    [blaze.fhir.hash.spec]
+    [clojure.spec.alpha :as s]))
+
+
+(s/fdef pao/index-entry
+  :args (s/cat :patient-id :blaze.db/id-byte-string
+               :tid :blaze.db/tid
+               :id :blaze.db/id-byte-string
+               :t :blaze.db/t
+               :hash :blaze.resource/hash
+               :num-changes nat-int?
+               :op keyword?)
+  :ret :blaze.db.kv/put-entry-w-cf)
+
+
+(s/fdef pao/last-change-t
+  :args (s/cat :paoi :blaze.db/kv-iterator
+               :patient-id :blaze.db/id-byte-string
+               :t :blaze.db/t)
+  :ret (s/nilable :blaze.db/t))
diff --git a/modules/db/test/blaze/db/impl/index/patient_as_of_test_util.clj b/modules/db/test/blaze/db/impl/index/patient_as_of_test_util.clj
new file mode 100644
index 000000000..cc35f6710
--- /dev/null
+++ b/modules/db/test/blaze/db/impl/index/patient_as_of_test_util.clj
@@ -0,0 +1,16 @@
+(ns blaze.db.impl.index.patient-as-of-test-util
+  (:require
+    [blaze.byte-buffer :as bb]
+    [blaze.byte-string :as bs]
+    [blaze.db.impl.codec :as codec]))
+
+
+(set! *unchecked-math* :warn-on-boxed)
+
+
+(defn decode-key [patient-id-len byte-array]
+  (let [buf (bb/wrap byte-array)]
+    {:patient-id (codec/id-string (bs/from-byte-buffer! buf patient-id-len))
+     :t (codec/descending-long (bb/get-long! buf))
+     :type (codec/tid->type (bb/get-int! buf))
+     :id (codec/id-string (bs/from-byte-buffer! buf (bb/remaining buf)))}))
diff --git a/modules/db/test/blaze/db/node/patient_as_of_index_spec.clj b/modules/db/test/blaze/db/node/patient_as_of_index_spec.clj
new file mode 100644
index 000000000..9b3595a1f
--- /dev/null
+++ b/modules/db/test/blaze/db/node/patient_as_of_index_spec.clj
@@ -0,0 +1,15 @@
+(ns blaze.db.node.patient-as-of-index-spec
+  (:require
+    [blaze.db.kv.spec]
+    [blaze.db.node.patient-as-of-index :as node-pao]
+    [blaze.db.node.tx-indexer-spec]
+    [blaze.db.spec]
+    [blaze.db.tx-log.spec]
+    [clojure.spec.alpha :as s]
+    [cognitect.anomalies :as anom]))
+
+
+(s/fdef node-pao/index-entries
+  :args (s/cat :node :blaze.db/node
+               :tx-data :blaze.db/tx-data)
+  :ret (s/or :entries (s/coll-of :blaze.db.kv/put-entry) :anomaly ::anom/anomaly))
diff --git a/modules/db/test/blaze/db/node/patient_as_of_index_test.clj b/modules/db/test/blaze/db/node/patient_as_of_index_test.clj
new file mode 100644
index 000000000..c39a8ab67
--- /dev/null
+++ b/modules/db/test/blaze/db/node/patient_as_of_index_test.clj
@@ -0,0 +1,49 @@
+(ns blaze.db.node.patient-as-of-index-test
+  (:require
+    [blaze.db.impl.index.patient-as-of :as pao]
+    [blaze.db.impl.index.patient-as-of-test-util :as pao-tu]
+    [blaze.db.impl.index.rts-as-of-test-util :as rts-tu]
+    [blaze.db.node.patient-as-of-index :as node-pao]
+    [blaze.db.node.patient-as-of-index-spec]
+    [blaze.db.test-util :refer [config with-system-data]]
+    [blaze.fhir.hash :as hash]
+    [blaze.test-util :as tu]
+    [clojure.spec.test.alpha :as st]
+    [clojure.test :as test :refer [deftest]]
+    [juxt.iota :refer [given]]
+    [taoensso.timbre :as log])
+  (:import
+    [java.nio.charset StandardCharsets]
+    [java.time Instant]))
+
+
+(st/instrument)
+(log/set-level! :trace)
+
+
+(test/use-fixtures :each tu/fixture)
+
+
+(def patient-0 {:fhir/type :fhir/Patient :id "0"})
+(def observation-0 {:fhir/type :fhir/Observation :id "0"
+                    :subject #fhir/Reference{:reference "Patient/0"}})
+(def hash-observation-0 (hash/generate observation-0))
+
+
+(deftest patient-as-of-index-entries-test
+  (with-system-data [{:blaze.db/keys [node]} config]
+    [[[:put patient-0]]]
+
+    (given (node-pao/index-entries
+             node
+             {:t 2
+              :instant Instant/EPOCH
+              :tx-cmds [{:op "put" :type "Observation" :id "0"
+                         :hash hash-observation-0 :refs [["Patient" "0"]]}]})
+      count := 2
+      [0 0] := :patient-as-of-index
+      [0 1 (partial pao-tu/decode-key 1)] := {:patient-id "0" :t 2 :type "Observation" :id "0"}
+      [0 2 rts-tu/decode-val] := {:hash hash-observation-0 :num-changes 1 :op :put}
+
+      [1 0 #(String. ^bytes % StandardCharsets/ISO_8859_1)] := "patient-as-of-state"
+      [1 1 pao/decode-state] := {:type :building :t 2})))
diff --git a/modules/db/test/blaze/db/node/tx_indexer/verify_spec.clj b/modules/db/test/blaze/db/node/tx_indexer/verify_spec.clj
index 6e1bc81f4..78d026428 100644
--- a/modules/db/test/blaze/db/node/tx_indexer/verify_spec.clj
+++ b/modules/db/test/blaze/db/node/tx_indexer/verify_spec.clj
@@ -8,6 +8,7 @@
     [blaze.db.impl.index.type-stats-spec]
     [blaze.db.kv.spec]
     [blaze.db.node.tx-indexer.verify :as verify]
+    [blaze.db.search-param-registry.spec]
     [blaze.db.spec]
     [blaze.db.tx-log.spec]
     [clojure.spec.alpha :as s]
@@ -15,6 +16,9 @@
 
 
 (s/fdef verify/verify-tx-cmds
-  :args (s/cat :db-before :blaze.db/db :t :blaze.db/t :cmds :blaze.db/tx-cmds)
+  :args (s/cat :search-param-registry :blaze.db/search-param-registry
+               :db-before :blaze.db/db
+               :t :blaze.db/t
+               :cmds :blaze.db/tx-cmds)
   :ret (s/or :entries (s/coll-of :blaze.db.kv/put-entry)
              :anomaly ::anom/anomaly))
diff --git a/modules/db/test/blaze/db/node/tx_indexer/verify_test.clj b/modules/db/test/blaze/db/node/tx_indexer/verify_test.clj
index 7bb1bc8a8..4e89e05d7 100644
--- a/modules/db/test/blaze/db/node/tx_indexer/verify_test.clj
+++ b/modules/db/test/blaze/db/node/tx_indexer/verify_test.clj
@@ -2,6 +2,7 @@
   (:require
     [blaze.db.api :as d]
     [blaze.db.impl.codec :as codec]
+    [blaze.db.impl.index.patient-as-of-test-util :as pao-tu]
     [blaze.db.impl.index.resource-as-of-test-util :as rao-tu]
     [blaze.db.impl.index.rts-as-of-test-util :as rts-tu]
     [blaze.db.impl.index.system-as-of-test-util :as sao-tu]
@@ -14,7 +15,7 @@
     [blaze.db.node.tx-indexer.verify :as verify]
     [blaze.db.node.tx-indexer.verify-spec]
     [blaze.db.search-param-registry]
-    [blaze.db.test-util :refer [config with-system-data]]
+    [blaze.db.test-util :refer [config search-param-registry with-system-data]]
     [blaze.db.tx-cache]
     [blaze.db.tx-log.local]
     [blaze.fhir.hash :as hash]
@@ -44,6 +45,10 @@
 (def patient-1 {:fhir/type :fhir/Patient :id "1"})
 (def patient-2 {:fhir/type :fhir/Patient :id "2"
                 :identifier [#fhir/Identifier{:value "120426"}]})
+(def observation-0 {:fhir/type :fhir/Observation :id "0"
+                    :subject #fhir/Reference{:reference "Patient/0"}})
+(def allergy-intolerance-0 {:fhir/type :fhir/AllergyIntolerance :id "0"
+                            :patient #fhir/Reference{:reference "Patient/0"}})
 
 
 (deftest verify-tx-cmds-test
@@ -53,6 +58,7 @@
               if-none-match [nil "*"]]
         (with-system [{:blaze.db/keys [node]} config]
           (given (verify/verify-tx-cmds
+                   search-param-registry
                    (d/db node) 1
                    [(cond-> {:op (name op) :type "Patient" :id "0" :hash hash}
                       if-none-match
@@ -80,13 +86,55 @@
             [4 1 ss-tu/decode-key] := {:t 1}
             [4 2 ss-tu/decode-val] := {:total 1 :num-changes 1})))))
 
-  (testing "adding a second version of a patient to a store containing it already"
+  (testing "adding one observation to a store containing its Patient already"
+    (let [hash (hash/generate observation-0)]
+      (doseq [op [:create :put]
+              if-none-match [nil "*"]]
+        (with-system-data [{:blaze.db/keys [node]} config]
+          [[[:put patient-0]]]
+
+          (given (verify/verify-tx-cmds
+                   search-param-registry
+                   (d/db node) 2
+                   [(cond-> {:op (name op) :type "Observation" :id "0"
+                             :hash hash :refs [["Patient" "0"]]}
+                      if-none-match
+                      (assoc :if-none-match if-none-match))])
+
+            count := 6
+
+            [0 0] := :resource-as-of-index
+            [0 1 rao-tu/decode-key] := {:type "Observation" :id "0" :t 2}
+            [0 2 rts-tu/decode-val] := {:hash hash :num-changes 1 :op op}
+
+            [1 0] := :type-as-of-index
+            [1 1 tao-tu/decode-key] := {:type "Observation" :t 2 :id "0"}
+            [1 2 rts-tu/decode-val] := {:hash hash :num-changes 1 :op op}
+
+            [2 0] := :system-as-of-index
+            [2 1 sao-tu/decode-key] := {:t 2 :type "Observation" :id "0"}
+            [2 2 rts-tu/decode-val] := {:hash hash :num-changes 1 :op op}
+
+            [3 0] := :patient-as-of-index
+            [3 1 (partial pao-tu/decode-key 1)] := {:patient-id "0" :t 2 :type "Observation" :id "0"}
+            [3 2 rts-tu/decode-val] := {:hash hash :num-changes 1 :op op}
+
+            [4 0] := :type-stats-index
+            [4 1 ts-tu/decode-key] := {:type "Observation" :t 2}
+            [4 2 ts-tu/decode-val] := {:total 1 :num-changes 1}
+
+            [5 0] := :system-stats-index
+            [5 1 ss-tu/decode-key] := {:t 2}
+            [5 2 ss-tu/decode-val] := {:total 2 :num-changes 2})))))
+
+  (testing "adding a second version of a Patient to a store containing it already"
     (let [hash (hash/generate patient-0-v2)]
       (doseq [if-match [nil 1 [1] [1 2]]]
         (with-system-data [{:blaze.db/keys [node]} config]
           [[[:put patient-0]]]
 
           (given (verify/verify-tx-cmds
+                   search-param-registry
                    (d/db node) 2
                    [(cond-> {:op "put" :type "Patient" :id "0" :hash hash}
                       if-match
@@ -122,6 +170,7 @@
            [[:delete "Patient" "0"]]]
 
           (given (verify/verify-tx-cmds
+                   search-param-registry
                    (d/db node) 3
                    [(cond-> {:op "put" :type "Patient" :id "0" :hash hash}
                       if-match
@@ -154,6 +203,7 @@
       [[[:put patient-0]]]
 
       (is (empty? (verify/verify-tx-cmds
+                    search-param-registry
                     (d/db node) 2
                     [{:op "put" :type "Patient" :id "0"
                       :hash (hash/generate patient-0)}])))))
@@ -162,7 +212,10 @@
     (with-system [{:blaze.db/keys [node]} config]
 
       (let [tx-cmd {:op "keep" :type "Patient" :id "0" :hash (hash/generate patient-0)}]
-        (given (verify/verify-tx-cmds (d/db node) 1 [tx-cmd])
+        (given (verify/verify-tx-cmds
+                 search-param-registry
+                 (d/db node) 1
+                 [tx-cmd])
           ::anom/category := ::anom/conflict
           ::anom/message := "Keep failed on `Patient/0`."
           :blaze.db/tx-cmd := tx-cmd))))
@@ -173,7 +226,10 @@
        [[:put patient-0-v2]]]
 
       (let [tx-cmd {:op "keep" :type "Patient" :id "0" :hash (hash/generate patient-0)}]
-        (given (verify/verify-tx-cmds (d/db node) 1 [tx-cmd])
+        (given (verify/verify-tx-cmds
+                 search-param-registry
+                 (d/db node) 1
+                 [tx-cmd])
           ::anom/category := ::anom/conflict
           ::anom/message := "Keep failed on `Patient/0`."
           :blaze.db/tx-cmd := tx-cmd))))
@@ -189,6 +245,7 @@
                         :hash (hash/generate patient-0-v2)
                         :if-match if-match}]
             (given (verify/verify-tx-cmds
+                     search-param-registry
                      (d/db node) 1
                      [tx-cmd])
               ::anom/category := ::anom/conflict
@@ -196,7 +253,7 @@
               :http/status := 412
               :blaze.db/tx-cmd := tx-cmd))))))
 
-  (testing "keeping a non-matching hash and non-matching if-match patient fails"
+  (testing "keeping a non-matching hash and non-matching if-match Patient fails"
     (with-system-data [{:blaze.db/keys [node]} config]
       [[[:put patient-0]]
        [[:put patient-0-v2]]]
@@ -206,7 +263,10 @@
           (let [tx-cmd {:op "keep" :type "Patient" :id "0"
                         :hash (hash/generate patient-0)
                         :if-match if-match}]
-            (given (verify/verify-tx-cmds (d/db node) 1 [tx-cmd])
+            (given (verify/verify-tx-cmds
+                     search-param-registry
+                     (d/db node) 1
+                     [tx-cmd])
               ::anom/category := ::anom/conflict
               ::anom/message := "Precondition `W/\"3\"` failed on `Patient/0`."
               :http/status := 412
@@ -219,6 +279,7 @@
       (testing "with different if-matches"
         (doseq [if-match [nil 1 [1] [1 2]]]
           (is (empty? (verify/verify-tx-cmds
+                        search-param-registry
                         (d/db node) 1
                         [(cond->
                            {:op "keep" :type "Patient" :id "0"
@@ -229,6 +290,7 @@
   (testing "deleting a Patient from an empty store"
     (with-system [{:blaze.db/keys [node]} config]
       (given (verify/verify-tx-cmds
+               search-param-registry
                (d/db node) 1
                [{:op "delete" :type "Patient" :id "0"}])
 
@@ -259,6 +321,7 @@
       [[[:delete "Patient" "0"]]]
 
       (given (verify/verify-tx-cmds
+               search-param-registry
                (d/db node) 2
                [{:op "delete" :type "Patient" :id "0"}])
 
@@ -289,6 +352,7 @@
       [[[:put patient-0]]]
 
       (given (verify/verify-tx-cmds
+               search-param-registry
                (d/db node) 2
                [{:op "delete" :type "Patient" :id "0"}])
 
@@ -314,12 +378,85 @@
         [4 1 ss-tu/decode-key] := {:t 2}
         [4 2 ss-tu/decode-val] := {:total 0 :num-changes 2})))
 
-  (testing "adding a second patient to a store containing already one"
+  (testing "deleting an existing Observation"
+    (with-system-data [{:blaze.db/keys [node]} config]
+      [[[:put patient-0]
+        [:put observation-0]]]
+
+      (given (verify/verify-tx-cmds
+               search-param-registry
+               (d/db node) 2
+               [{:op "delete" :type "Observation" :id "0"}])
+
+        count := 6
+
+        [0 0] := :resource-as-of-index
+        [0 1 rao-tu/decode-key] := {:type "Observation" :id "0" :t 2}
+        [0 2 rts-tu/decode-val] := {:hash hash/deleted-hash :num-changes 2 :op :delete}
+
+        [1 0] := :type-as-of-index
+        [1 1 tao-tu/decode-key] := {:type "Observation" :t 2 :id "0"}
+        [1 2 rts-tu/decode-val] := {:hash hash/deleted-hash :num-changes 2 :op :delete}
+
+        [2 0] := :system-as-of-index
+        [2 1 sao-tu/decode-key] := {:t 2 :type "Observation" :id "0"}
+        [2 2 rts-tu/decode-val] := {:hash hash/deleted-hash :num-changes 2 :op :delete}
+
+        [3 0] := :patient-as-of-index
+        [3 1 (partial pao-tu/decode-key 1)] := {:patient-id "0" :t 2 :type "Observation" :id "0"}
+        [3 2 rts-tu/decode-val] := {:hash hash/deleted-hash :num-changes 2 :op :delete}
+
+        [4 0] := :type-stats-index
+        [4 1 ts-tu/decode-key] := {:type "Observation" :t 2}
+        [4 2 ts-tu/decode-val] := {:total 0 :num-changes 2}
+
+        [5 0] := :system-stats-index
+        [5 1 ss-tu/decode-key] := {:t 2}
+        [5 2 ss-tu/decode-val] := {:total 1 :num-changes 3})))
+
+  (testing "deleting an existing AllergyIntolerance"
+    (with-system-data [{:blaze.db/keys [node]} config]
+      [[[:put patient-0]
+        [:put allergy-intolerance-0]]]
+
+      (given (verify/verify-tx-cmds
+               search-param-registry
+               (d/db node) 2
+               [{:op "delete" :type "AllergyIntolerance" :id "0"}])
+
+        count := 6
+
+        [0 0] := :resource-as-of-index
+        [0 1 rao-tu/decode-key] := {:type "AllergyIntolerance" :id "0" :t 2}
+        [0 2 rts-tu/decode-val] := {:hash hash/deleted-hash :num-changes 2 :op :delete}
+
+        [1 0] := :type-as-of-index
+        [1 1 tao-tu/decode-key] := {:type "AllergyIntolerance" :t 2 :id "0"}
+        [1 2 rts-tu/decode-val] := {:hash hash/deleted-hash :num-changes 2 :op :delete}
+
+        [2 0] := :system-as-of-index
+        [2 1 sao-tu/decode-key] := {:t 2 :type "AllergyIntolerance" :id "0"}
+        [2 2 rts-tu/decode-val] := {:hash hash/deleted-hash :num-changes 2 :op :delete}
+
+        [3 0] := :patient-as-of-index
+        [3 1 (partial pao-tu/decode-key 1)] := {:patient-id "0" :t 2 :type "AllergyIntolerance" :id "0"}
+        [3 2 rts-tu/decode-val] := {:hash hash/deleted-hash :num-changes 2 :op :delete}
+
+        [4 0] := :type-stats-index
+        [4 1 ts-tu/decode-key] := {:type "AllergyIntolerance" :t 2}
+        [4 2 ts-tu/decode-val] := {:total 0 :num-changes 2}
+
+        [5 0] := :system-stats-index
+        [5 1 ss-tu/decode-key] := {:t 2}
+        [5 2 ss-tu/decode-val] := {:total 1 :num-changes 3})))
+
+  (testing "adding a second Patient to a store containing already one"
     (let [hash (hash/generate patient-1)]
       (with-system-data [{:blaze.db/keys [node]} config]
         [[[:put patient-0]]]
 
         (given (verify/verify-tx-cmds
+                 search-param-registry
                  (d/db node) 2
                  [{:op "put" :type "Patient" :id "1" :hash hash}])
 
@@ -351,6 +488,7 @@
         [[[:put patient-0]]]
 
         (given (verify/verify-tx-cmds
+                 search-param-registry
                  (d/db node) 2
                  [{:op "put" :type "Patient" :id "0"
                    :hash (hash/generate patient-0)
@@ -364,6 +502,7 @@
         [[[:put patient-0]]]
 
         (given (verify/verify-tx-cmds
+                 search-param-registry
                  (d/db node) 2
                  [{:op "put" :type "Patient" :id "0"
                    :hash (hash/generate patient-0)
@@ -377,6 +516,7 @@
         [[[:put patient-0]]]
 
         (given (verify/verify-tx-cmds
+                 search-param-registry
                  (d/db node) 2
                  [{:op "put" :type "Patient" :id "0"
                    :hash (hash/generate patient-0)
@@ -394,6 +534,7 @@
                  :birthDate #fhir/date"2020"}]]]
 
         (given (verify/verify-tx-cmds
+                 search-param-registry
                  (d/db node) 2
                  [{:op "create" :type "Patient" :id "foo"
                    :hash (hash/generate patient-0)
@@ -409,6 +550,7 @@
         (is
           (empty?
             (verify/verify-tx-cmds
+              search-param-registry
               (d/db node) 2
               [{:op "create" :type "Patient" :id "0"
                 :hash (hash/generate patient-0)
@@ -420,6 +562,7 @@
 
         (given
           (verify/verify-tx-cmds
+            search-param-registry
             (d/db node) 2
             [{:op "delete" :type "Patient" :id "2"}
              {:op "create" :type "Patient" :id "0"
@@ -435,6 +578,7 @@
            [[:delete "Patient" "0"]]]
 
           (given (verify/verify-tx-cmds
+                   search-param-registry
                    (d/db node) 3
                    [{:op "put" :type "Patient" :id "0" :hash hash}])
 
diff --git a/modules/db/test/blaze/db/node/tx_indexer_spec.clj b/modules/db/test/blaze/db/node/tx_indexer_spec.clj
index 923a95260..f68083076 100644
--- a/modules/db/test/blaze/db/node/tx_indexer_spec.clj
+++ b/modules/db/test/blaze/db/node/tx_indexer_spec.clj
@@ -3,6 +3,7 @@
     [blaze.db.kv.spec]
     [blaze.db.node.tx-indexer :as tx-indexer]
     [blaze.db.node.tx-indexer.verify-spec]
+    [blaze.db.search-param-registry.spec]
     [blaze.db.spec]
     [blaze.db.tx-log.spec]
     [clojure.spec.alpha :as s]
@@ -10,5 +11,7 @@
 
 
 (s/fdef tx-indexer/index-tx
-  :args (s/cat :db-before :blaze.db/db :tx-data :blaze.db/tx-data)
+  :args (s/cat :search-param-registry :blaze.db/search-param-registry
+               :db-before :blaze.db/db
+               :tx-data :blaze.db/tx-data)
   :ret (s/or :entries (s/coll-of :blaze.db.kv/put-entry) :anomaly ::anom/anomaly))
diff --git a/modules/db/test/blaze/db/node_test.clj b/modules/db/test/blaze/db/node_test.clj
index 0ff5da515..99fc4b702 100644
--- a/modules/db/test/blaze/db/node_test.clj
+++ b/modules/db/test/blaze/db/node_test.clj
@@ -6,11 +6,13 @@
     [blaze.db.api :as d]
     [blaze.db.api-spec]
     [blaze.db.impl.db-spec]
+    [blaze.db.impl.index.patient-as-of :as pao]
     [blaze.db.impl.index.tx-success :as tx-success]
     [blaze.db.kv :as kv]
     [blaze.db.kv.mem-spec]
     [blaze.db.node :as node]
     [blaze.db.node-spec]
+    [blaze.db.node.patient-as-of-index-spec]
     [blaze.db.node.resource-indexer :as resource-indexer]
     [blaze.db.node.tx-indexer :as-alias tx-indexer]
     [blaze.db.node.version :as version]
@@ -281,3 +283,13 @@
 (deftest existing-data-with-compatible-version
   (with-system [{:blaze.db/keys [node]} (with-index-store-version config 0)]
     (is node)))
+
+
+(deftest patient-as-of-index-state-test
+  (testing "the state is set to current on a fresh start of the node"
+    (with-system [{:blaze.db/keys [node]} config]
+      ;; Wait for index building finished
+      (Thread/sleep 100)
+
+      (given (pao/state (:kv-store node))
+        :type := :current))))
diff --git a/modules/db/test/blaze/db/resource_cache_test.clj b/modules/db/test/blaze/db/resource_cache_test.clj
index 821e9da6e..08a868aab 100644
--- a/modules/db/test/blaze/db/resource_cache_test.clj
+++ b/modules/db/test/blaze/db/resource_cache_test.clj
@@ -1,6 +1,6 @@
 (ns blaze.db.resource-cache-test
   (:require
-    [blaze.db.cache-collector.protocols :as ccp]
+    [blaze.cache-collector.protocols :as ccp]
     [blaze.db.kv :as kv]
     [blaze.db.kv.mem]
     [blaze.db.resource-cache :as resource-cache]
diff --git a/modules/db/test/blaze/db/search_param_registry_test.clj b/modules/db/test/blaze/db/search_param_registry_test.clj
index 59dfa68b6..fb8bc8031 100644
--- a/modules/db/test/blaze/db/search_param_registry_test.clj
+++ b/modules/db/test/blaze/db/search_param_registry_test.clj
@@ -194,12 +194,17 @@
 (deftest compartment-resources-test
   (testing "Patient"
     (with-system [{:blaze.db/keys [search-param-registry]} config]
-      (given (sr/compartment-resources search-param-registry "Patient")
-        count := 100
-        [0] := ["Account" "subject"]
-        [1] := ["AdverseEvent" "subject"]
-        [2] := ["AllergyIntolerance" "patient"]
-        [3] := ["AllergyIntolerance" "recorder"]
-        [4] := ["AllergyIntolerance" "asserter"]
-        [5] := ["Appointment" "actor"]
-        [99] := ["VisionPrescription" "patient"]))))
+      (testing "all resource types"
+        (given (sr/compartment-resources search-param-registry "Patient")
+          count := 100
+          [0] := ["Account" "subject"]
+          [1] := ["AdverseEvent" "subject"]
+          [2] := ["AllergyIntolerance" "patient"]
+          [3] := ["AllergyIntolerance" "recorder"]
+          [4] := ["AllergyIntolerance" "asserter"]
+          [5] := ["Appointment" "actor"]
+          [99] := ["VisionPrescription" "patient"]))
+
+      (testing "only Observation codes"
+        (is (= (sr/compartment-resources search-param-registry "Patient" "Observation")
+               ["subject" "performer"]))))))
diff --git a/modules/db/test/blaze/db/test_util.clj b/modules/db/test/blaze/db/test_util.clj
index ea7ca5516..38f383087 100644
--- a/modules/db/test/blaze/db/test_util.clj
+++ b/modules/db/test/blaze/db/test_util.clj
@@ -30,6 +30,7 @@
     :kv-store (ig/ref :blaze.db/index-kv-store)
     :resource-indexer (ig/ref :blaze.db.node/resource-indexer)
     :search-param-registry search-param-registry
+    :scheduler (ig/ref :blaze/scheduler)
     :poll-timeout (time/millis 10)}
 
    ::tx-log/local
@@ -60,6 +61,7 @@
      :resource-as-of-index nil
      :type-as-of-index nil
      :system-as-of-index nil
+     :patient-as-of-index nil
      :type-stats-index nil
      :system-stats-index nil}}
 
@@ -78,7 +80,9 @@
     :search-param-registry search-param-registry
     :executor (ig/ref :blaze.db.node.resource-indexer/executor)}
 
-   :blaze.db.node.resource-indexer/executor {}})
+   :blaze.db.node.resource-indexer/executor {}
+
+   :blaze/scheduler {}})
 
 
 (defmacro with-system-data
diff --git a/modules/executor/src/blaze/executors.clj b/modules/executor/src/blaze/executors.clj
index f8c4695f9..63c943834 100644
--- a/modules/executor/src/blaze/executors.clj
+++ b/modules/executor/src/blaze/executors.clj
@@ -50,6 +50,12 @@
   (format name-template (swap! thread-counter inc)))
 
 
+(defn- thread-factory [counter name-template]
+  (reify ThreadFactory
+    (newThread [_ r]
+      (Thread. ^Runnable r ^String (thread-name! counter name-template)))))
+
+
 (defn cpu-bound-pool
   "Returns a thread pool with a fixed number of threads which is the number of
   available processors."
@@ -57,10 +63,7 @@
   (let [thread-counter (atom 0)]
     (Executors/newFixedThreadPool
       (.availableProcessors (Runtime/getRuntime))
-      (reify ThreadFactory
-        (newThread [_ r]
-          (Thread. ^Runnable r ^String (thread-name! thread-counter
-                                                     name-template)))))))
+      (thread-factory thread-counter name-template))))
 
 
 (defn io-pool
@@ -70,10 +73,14 @@
   (let [thread-counter (atom 0)]
     (Executors/newFixedThreadPool
       n
-      (reify ThreadFactory
-        (newThread [_ r]
-          (Thread. ^Runnable r ^String (thread-name! thread-counter
-                                                     name-template)))))))
+      (thread-factory thread-counter name-template))))
+
+
+(defn scheduled-pool [n name-template]
+  (let [thread-counter (atom 0)]
+    (Executors/newScheduledThreadPool
+      n
+      (thread-factory thread-counter name-template))))
 
 
 (defn single-thread-executor
diff --git a/modules/operation-measure-evaluate-measure/.clj-kondo/config.edn b/modules/operation-measure-evaluate-measure/.clj-kondo/config.edn
index 2acbb21c8..f493241e1 100644
--- a/modules/operation-measure-evaluate-measure/.clj-kondo/config.edn
+++ b/modules/operation-measure-evaluate-measure/.clj-kondo/config.edn
@@ -26,6 +26,7 @@
   :consistent-alias
   {:aliases
    {blaze.db.api d
+    blaze.elm.compiler.expr-cache ec
     blaze.elm.compiler.external-data ed
     blaze.elm.expression expr
     cognitect.anomalies anom
diff --git a/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure.clj b/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure.clj
index f10a60281..2e4256aa5 100644
--- a/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure.clj
+++ b/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure.clj
@@ -5,6 +5,10 @@
     [blaze.async.comp :as ac]
     [blaze.coll.core :as coll]
     [blaze.db.api :as d]
+    [blaze.elm.compiler.expr-cache :as ec]
+    [blaze.elm.compiler.macros]
+    [blaze.elm.expression :as-alias expr]
+    [blaze.elm.expression.spec]
     [blaze.executors :as ex]
     [blaze.fhir.operation.evaluate-measure.measure :as measure]
     [blaze.fhir.operation.evaluate-measure.measure.spec]
@@ -24,6 +28,7 @@
     [ring.util.response :as ring]
     [taoensso.timbre :as log])
   (:import
+    [com.github.benmanes.caffeine.cache Caffeine Weigher]
     [java.util.concurrent TimeUnit]))
 
 
@@ -130,6 +135,7 @@
 
 (defmethod ig/pre-init-spec ::handler [_]
   (s/keys :req-un [:blaze.db/node ::executor :blaze/clock :blaze/rng-fn]
+          :opt [::expr/cache]
           :opt-un [::timeout]))
 
 
@@ -138,6 +144,23 @@
   (wrap-coerce-params (handler context)))
 
 
+(defmethod ig/pre-init-spec ::expr-cache [_]
+  (s/keys :opt-un [::max-size]))
+
+
+(defmethod ig/init-key ::expr-cache
+  [_ {:keys [max-size] :or {max-size 0}}]
+  (log/info "Create CQL expression cache with a size of" max-size "expressions")
+  (-> (Caffeine/newBuilder)
+      (.weigher
+        (reify Weigher
+          (weigh [_ _ cache]
+            (ec/mem-size cache))))
+      (.maximumWeight max-size)
+      (.recordStats)
+      (.buildAsync)))
+
+
 (defmethod ig/pre-init-spec ::timeout [_]
   (s/keys :req-un [:blaze.fhir.operation.evaluate-measure.timeout/millis]))
 
@@ -179,3 +202,23 @@
 
 (reg-collector ::evaluate-duration-seconds
   measure/evaluate-duration-seconds)
+
+
+(reg-collector ::bloom-filter-creation-duration-seconds
+  blaze.elm.compiler.macros/bloom-filter-creation-duration-seconds)
+
+
+(reg-collector ::bloom-filter-useful-total
+  blaze.elm.compiler.macros/bloom-filter-useful-total)
+
+
+(reg-collector ::bloom-filter-not-useful-total
+  blaze.elm.compiler.macros/bloom-filter-not-useful-total)
+
+
+(reg-collector ::bloom-filter-false-positive-total
+  blaze.elm.compiler.macros/bloom-filter-false-positive-total)
+
+
+(reg-collector ::bloom-filter-bytes
+  ec/bloom-filter-bytes)
diff --git a/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/measure.clj b/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/measure.clj
index 62cea1e41..c56c5db7a 100644
--- a/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/measure.clj
+++ b/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/measure.clj
@@ -4,8 +4,10 @@
     [blaze.coll.core :as coll]
     [blaze.cql-translator :as cql-translator]
     [blaze.db.api :as d]
+    [blaze.elm.compiler :as c]
     [blaze.elm.compiler.external-data :as ed]
     [blaze.elm.compiler.library :as library]
+    [blaze.elm.expression :as-alias expr]
     [blaze.fhir.operation.evaluate-measure.measure.population :as population]
     [blaze.fhir.operation.evaluate-measure.measure.stratifier :as stratifier]
     [blaze.fhir.operation.evaluate-measure.measure.util :as u]
@@ -83,10 +85,10 @@
   using `node`.
 
   Returns an anomaly on errors."
-  [node library]
+  [node library opts]
   (when-ok [cql-code (extract-cql-code library)
             library (translate cql-code)]
-    (library/compile-library node library {})))
+    (library/compile-library node library opts)))
 
 
 (defn- compile-library
@@ -94,12 +96,12 @@
   using `node`.
 
   Returns an anomaly on errors."
-  {:arglists '([node library])}
-  [node {:keys [id] :as library}]
+  {:arglists '([node library opts])}
+  [node {:keys [id] :as library} opts]
   (log/debug (format "Start compiling Library with ID `%s`..." id))
   (let [timer (prom/timer compile-duration-seconds)]
     (try
-      (compile-library* node library)
+      (compile-library* node library opts)
       (finally
         (let [duration (prom/observe-duration! timer)]
           (log/debug
@@ -135,10 +137,10 @@
   compilation.
 
   Returns an anomaly on errors."
-  [db measure]
+  [db measure opts]
   (if-let [library-ref (-> measure :library first type/value)]
     (if-let [library (find-library db library-ref)]
-      (compile-library (d/node db) library)
+      (compile-library (d/node db) library opts)
       (ba/incorrect
         (format "The Library resource with canonical URI `%s` was not found." library-ref)
         :fhir/issue "value"
@@ -335,13 +337,25 @@
     (subject-handle* db subject-type subject-ref)))
 
 
+(defn- attach-cache* [context [name expr]]
+  [name (update expr :expression (partial c/attach-cache context))])
+
+
+(defn- attach-cache [context expression-defs]
+  (into {} (map (partial attach-cache* context)) expression-defs))
+
+
 (defn- enhance-context
-  [{:keys [clock db timeout] :as context :or {timeout (time/hours 1)}} measure
+  [{:keys [clock db timeout]
+    ::expr/keys [cache]
+    :or {timeout (time/hours 1)}
+    :as context} measure
    {:keys [report-type subject-ref]}]
   (let [subject-type (subject-type measure)
         now (now clock)
         timeout-instant (time/instant (time/plus now timeout))]
-    (when-ok [{:keys [expression-defs function-defs parameter-default-values]} (compile-primary-library db measure)
+    (when-ok [{:keys [expression-defs function-defs parameter-default-values]}
+              (compile-primary-library db measure {})
               subject-handle (some->> subject-ref (subject-handle db subject-type))]
       (cond->
         (assoc context
@@ -349,7 +363,16 @@
           :now now
           :timeout-eclipsed? #(not (.isBefore (.instant ^Clock clock) timeout-instant))
           :timeout timeout
-          :expression-defs expression-defs
+          :expression-defs
+          (if cache
+            (attach-cache
+              (assoc context
+                :db db
+                :now now
+                :expression-defs expression-defs
+                :parameters parameter-default-values)
+              expression-defs)
+            expression-defs)
           :function-defs function-defs
           :parameters parameter-default-values
           :subject-type subject-type
diff --git a/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/spec.clj b/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/spec.clj
index d8f3c7a3f..09e536443 100644
--- a/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/spec.clj
+++ b/modules/operation-measure-evaluate-measure/src/blaze/fhir/operation/evaluate_measure/spec.clj
@@ -14,6 +14,10 @@
   pos-int?)
 
 
+(s/def ::measure/max-size
+  nat-int?)
+
+
 (s/def ::measure/timeout
   time/duration?)
 
diff --git a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/cql/spec.clj b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/cql/spec.clj
index 8f7561a60..3a459c190 100644
--- a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/cql/spec.clj
+++ b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/cql/spec.clj
@@ -1,15 +1,12 @@
 (ns blaze.fhir.operation.evaluate-measure.cql.spec
   (:require
     [blaze.elm.compiler :as-alias compiler]
+    [blaze.elm.expression :as-alias expr]
     [blaze.fhir.operation.evaluate-measure.cql :as-alias cql]
     [clojure.spec.alpha :as s]
     [java-time.api :as time]))
 
 
-(s/def ::cql/now
-  time/offset-date-time?)
-
-
 (s/def ::cql/timeout-eclipsed?
   ifn?)
 
@@ -19,8 +16,10 @@
 
 
 (s/def ::cql/context
-  (s/keys :req-un [:blaze.db/db ::cql/now ::cql/timeout-eclipsed? ::cql/timeout
-                   ::compiler/expression-defs]))
+  (s/merge
+    ::expr/context
+    (s/keys :req-un [::cql/timeout-eclipsed? ::cql/timeout
+                     ::compiler/expression-defs])))
 
 
 (s/def ::cql/return-handles?
@@ -31,9 +30,5 @@
   (s/merge ::cql/context (s/keys :opt-un [::cql/return-handles?])))
 
 
-(s/def ::cql/parameters
-  (s/map-of string? any?))
-
-
 (s/def ::cql/evaluate-individual-expression-context
-  (s/merge ::cql/context (s/keys :opt-un [::cql/parameters])))
+  ::cql/context)
diff --git a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/cql_test.clj b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/cql_test.clj
index feba245fb..ac1e588b0 100644
--- a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/cql_test.clj
+++ b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/cql_test.clj
@@ -21,6 +21,7 @@
     [juxt.iota :refer [given]]
     [taoensso.timbre :as log])
   (:import
+    [com.github.benmanes.caffeine.cache Caffeine]
     [java.time Clock OffsetDateTime]))
 
 
@@ -104,6 +105,7 @@
   (let [{:keys [expression-defs function-defs]} (compile-library node library)]
     {:db (d/db node)
      :now (now fixed-clock)
+     ::expr/cache (.buildAsync (Caffeine/newBuilder))
      :timeout-eclipsed? (constantly false)
      :timeout (time/seconds 42)
      :expression-defs expression-defs
diff --git a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure/stratifier_test.clj b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure/stratifier_test.clj
index bedf1dc60..4c8d5191c 100644
--- a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure/stratifier_test.clj
+++ b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure/stratifier_test.clj
@@ -6,6 +6,7 @@
     [blaze.db.api :as d]
     [blaze.db.api-stub :refer [mem-node-config with-system-data]]
     [blaze.elm.compiler.library :as library]
+    [blaze.elm.expression :as-alias expr]
     [blaze.fhir.operation.evaluate-measure.measure.stratifier :as stratifier]
     [blaze.fhir.operation.evaluate-measure.measure.stratifier-spec]
     [blaze.fhir.operation.evaluate-measure.test-util :as em-tu]
diff --git a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure_spec.clj b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure_spec.clj
index f048a0485..4a3999e54 100644
--- a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure_spec.clj
+++ b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure_spec.clj
@@ -2,6 +2,8 @@
   (:require
     [blaze.cql-translator-spec]
     [blaze.db.spec]
+    [blaze.elm.expression :as-alias expr]
+    [blaze.elm.expression.spec]
     [blaze.fhir.operation.evaluate-measure.cql-spec]
     [blaze.fhir.operation.evaluate-measure.measure :as measure]
     [blaze.fhir.operation.evaluate-measure.measure.spec]
@@ -15,6 +17,12 @@
     [java.time.temporal Temporal]))
 
 
+(s/def ::context
+  (s/keys :req [:blaze/base-url ::reitit/router]
+          :opt [::expr/cache]
+          :req-un [:blaze/clock :blaze/rng-fn :blaze.db/db]))
+
+
 (defn- temporal? [x]
   (instance? Temporal x))
 
@@ -33,12 +41,6 @@
 
 
 (s/fdef measure/evaluate-measure
-  :args
-  (s/cat
-    :context (s/keys :req [:blaze/base-url ::reitit/router]
-                     :req-un [:blaze/clock :blaze/rng-fn :blaze.db/db])
-    :measure :blaze/resource
-    :params ::params)
-  :ret
-  (s/or :result (s/keys :req-un [:blaze/resource] :opt-un [:blaze.db/tx-ops])
-        :anomaly ::anom/anomaly))
+  :args (s/cat :context ::context :measure :blaze/resource :params ::params)
+  :ret (s/or :result (s/keys :req-un [:blaze/resource] :opt-un [:blaze.db/tx-ops])
+             :anomaly ::anom/anomaly))
diff --git a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure_test.clj b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure_test.clj
index b8e6490c5..b12e5c6e9 100644
--- a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure_test.clj
+++ b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure/measure_test.clj
@@ -3,6 +3,7 @@
     [blaze.anomaly :as ba]
     [blaze.db.api :as d]
     [blaze.db.api-stub :refer [mem-node-config with-system-data]]
+    [blaze.elm.expression :as-alias expr]
     [blaze.fhir.operation.evaluate-measure.measure :as measure]
     [blaze.fhir.operation.evaluate-measure.measure-spec]
     [blaze.fhir.operation.evaluate-measure.measure.population-spec]
@@ -22,6 +23,7 @@
     [reitit.core :as reitit]
     [taoensso.timbre :as log])
   (:import
+    [com.github.benmanes.caffeine.cache Caffeine]
     [java.nio.charset StandardCharsets]
     [java.util Base64]))
 
@@ -97,10 +99,11 @@
 
      (let [db (d/db node)
            context {:clock fixed-clock :rng-fn fixed-rng-fn :db db
+                    ::expr/cache (.buildAsync (Caffeine/newBuilder))
                     :blaze/base-url "" ::reitit/router router}
+           measure @(d/pull node (d/resource-handle db "Measure" "0"))
            period [#system/date"2000" #system/date"2020"]]
-       (measure/evaluate-measure context
-                                 @(d/pull node (d/resource-handle db "Measure" "0"))
+       (measure/evaluate-measure context measure
                                  {:period period :report-type report-type})))))
 
 
@@ -740,6 +743,7 @@
     [1 :population 0 :count] := 2)
 
   (given (first-stratifier-strata (evaluate "q29-stratifier-sample-material-type"))
+    count := 2
     [0 :value :text type/value] := "liquid"
     [0 :population 0 :count] := 1
     [1 :value :text type/value] := "tissue"
diff --git a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure_test.clj b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure_test.clj
index 30b741b5b..b8fb5c152 100644
--- a/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure_test.clj
+++ b/modules/operation-measure-evaluate-measure/test/blaze/fhir/operation/evaluate_measure_test.clj
@@ -4,6 +4,7 @@
     [blaze.async.comp :as ac]
     [blaze.db.api-stub :as api-stub :refer [with-system-data]]
     [blaze.db.resource-store :as rs]
+    [blaze.elm.expression :as-alias expr]
     [blaze.executors :as ex]
     [blaze.fhir.operation.evaluate-measure :as evaluate-measure]
     [blaze.fhir.operation.evaluate-measure.test-util :refer [wrap-error]]
@@ -99,6 +100,26 @@
       [:explain ::s/problems 3 :val] := ::invalid)))
 
 
+(deftest expr-cache-init-test
+  (testing "nil config"
+    (given-thrown (ig/init {::evaluate-measure/expr-cache nil})
+      :key := ::evaluate-measure/expr-cache
+      :reason := ::ig/build-failed-spec
+      [:explain ::s/problems 0 :pred] := `map?))
+
+  (testing "invalid millis"
+    (given-thrown (ig/init {::evaluate-measure/expr-cache {:max-size ::invalid}})
+      :key := ::evaluate-measure/expr-cache
+      :reason := ::ig/build-failed-spec
+      [:explain ::s/problems 0 :pred] := `nat-int?
+      [:explain ::s/problems 0 :val] := ::invalid))
+
+  (testing "init"
+    (with-system [{::evaluate-measure/keys [expr-cache]}
+                  {::evaluate-measure/expr-cache {:max-size 125509}}]
+      (is (s/valid? ::expr/cache expr-cache)))))
+
+
 (deftest timeout-init-test
   (testing "nil config"
     (given-thrown (ig/init {::evaluate-measure/timeout nil})
@@ -161,9 +182,11 @@
   (assoc api-stub/mem-node-config
     ::evaluate-measure/handler
     {:node (ig/ref :blaze.db/node)
+     ::expr/cache (ig/ref ::evaluate-measure/expr-cache)
      :executor (ig/ref :blaze.test/executor)
      :clock (ig/ref :blaze.test/fixed-clock)
      :rng-fn (ig/ref :blaze.test/fixed-rng-fn)}
+    ::evaluate-measure/expr-cache {}
     :blaze.test/executor {}
     :blaze.test/fixed-rng-fn {}))
 
diff --git a/modules/rest-api/src/blaze/rest_api/middleware/metrics.clj b/modules/rest-api/src/blaze/rest_api/middleware/metrics.clj
index 5c4fa53fe..c592e88eb 100644
--- a/modules/rest-api/src/blaze/rest_api/middleware/metrics.clj
+++ b/modules/rest-api/src/blaze/rest_api/middleware/metrics.clj
@@ -2,13 +2,13 @@
   (:require
     [blaze.util :as u]
     [clojure.string :as str]
-    [prometheus.alpha :as prom]))
+    [prometheus.alpha :as prom :refer [defcounter defhistogram]]))
 
 
 (set! *warn-on-reflection* true)
 
 
-(prom/defcounter requests-total
+(defcounter requests-total
   "Number of requests to this service.
    Distinguishes between the returned status code, the handler being used to
    process the request together with the http method."
@@ -17,7 +17,7 @@
   "code" "interaction" "method")
 
 
-(prom/defhistogram request-duration-seconds
+(defhistogram request-duration-seconds
   "The HTTP request latencies in seconds."
   {:namespace "http"
    :subsystem "fhir"}
diff --git a/modules/scheduler/src/blaze/scheduler.clj b/modules/scheduler/src/blaze/scheduler.clj
index 0a5aa8fae..7497856fd 100644
--- a/modules/scheduler/src/blaze/scheduler.clj
+++ b/modules/scheduler/src/blaze/scheduler.clj
@@ -7,13 +7,20 @@
     [java-time.api :as time]
     [taoensso.timbre :as log])
   (:import
-    [java.util.concurrent Executors Future ScheduledExecutorService TimeUnit]))
+    [java.util.concurrent Future ScheduledExecutorService TimeUnit]))
 
 
 (set! *warn-on-reflection* true)
 
 
-(defn schedule-at-fixed-rate [scheduler f initial-delay period]
+(defn submit [scheduler f]
+  (p/-submit scheduler f))
+
+
+(defn schedule-at-fixed-rate
+  "Schedules the function `f` to be called at a rate of `period` with an
+  `initial-delay`."
+  [scheduler f initial-delay period]
   (p/-schedule-at-fixed-rate scheduler f initial-delay period))
 
 
@@ -23,6 +30,9 @@
 
 (extend-protocol p/Scheduler
   ScheduledExecutorService
+  (-submit [scheduler f]
+    (.submit scheduler ^Runnable f))
+
   (-schedule-at-fixed-rate [scheduler f initial-delay period]
     (.scheduleAtFixedRate
       scheduler
@@ -35,7 +45,7 @@
 (defmethod ig/init-key :blaze/scheduler
   [_ _]
   (log/info "Start scheduler")
-  (Executors/newSingleThreadScheduledExecutor))
+  (ex/scheduled-pool 4 "scheduler-%d"))
 
 
 (defmethod ig/halt-key! :blaze/scheduler
@@ -45,3 +55,6 @@
   (if (ex/await-termination scheduler 10 TimeUnit/SECONDS)
     (log/info "Scheduler was stopped successfully")
     (log/warn "Got timeout while stopping the scheduler")))
+
+
+(derive :blaze/scheduler :blaze.metrics/thread-pool-executor)
diff --git a/modules/scheduler/src/blaze/scheduler/protocol.clj b/modules/scheduler/src/blaze/scheduler/protocol.clj
index 108dd768f..7a25c46ad 100644
--- a/modules/scheduler/src/blaze/scheduler/protocol.clj
+++ b/modules/scheduler/src/blaze/scheduler/protocol.clj
@@ -2,4 +2,5 @@
 
 
 (defprotocol Scheduler
+  (-submit [scheduler f])
   (-schedule-at-fixed-rate [scheduler f initial-delay period]))
diff --git a/profiling/blaze/profiling.clj b/profiling/blaze/profiling.clj
index 241b8305e..b39b1f3e8 100644
--- a/profiling/blaze/profiling.clj
+++ b/profiling/blaze/profiling.clj
@@ -1,10 +1,10 @@
 (ns blaze.profiling
   "Profiling namespace without test dependencies."
   (:require
-    [blaze.system :as system]
-    [blaze.db.cache-collector :as cc]
+    [blaze.cache-collector.protocols :as ccp]
     [blaze.db.kv.rocksdb :as rocksdb]
     [blaze.db.resource-cache :as resource-cache]
+    [blaze.system :as system]
     [clojure.tools.namespace.repl :refer [refresh]]
     [taoensso.timbre :as log]))
 
@@ -43,16 +43,21 @@
 
 ;; Transaction Cache
 (comment
-  (str (cc/-stats (:blaze.db/tx-cache system)))
+  (str (ccp/-stats (:blaze.db/tx-cache system)))
   (resource-cache/invalidate-all! (:blaze.db/tx-cache system))
   )
 
 ;; Resource Cache
 (comment
-  (str (cc/-stats (:blaze.db/resource-cache system)))
+  (str (ccp/-stats (:blaze.db/resource-cache system)))
   (resource-cache/invalidate-all! (:blaze.db/resource-cache system))
   )
 
+;; CQL Expression Cache
+(comment
+  (str (ccp/-stats (:blaze.fhir.operation.evaluate-measure/expr-cache system)))
+  )
+
 ;; DB
 (comment
   (str (system [:blaze.db.kv.rocksdb/stats :blaze.db.index-kv-store/stats]))
@@ -69,6 +74,7 @@
   (rocksdb/get-property index-db :resource-as-of-index "rocksdb.stats")
   (rocksdb/get-property index-db :type-as-of-index "rocksdb.stats")
   (rocksdb/get-property index-db :system-as-of-index "rocksdb.stats")
+  (rocksdb/get-property index-db :patient-as-of-index "rocksdb.stats")
   (rocksdb/get-property index-db :type-stats-index "rocksdb.stats")
   (rocksdb/get-property index-db :system-stats-index "rocksdb.stats")
 
diff --git a/resources/blaze.edn b/resources/blaze.edn
index 112e895f9..bbc5ed48f 100644
--- a/resources/blaze.edn
+++ b/resources/blaze.edn
@@ -162,6 +162,11 @@
 
   :blaze.fhir.operation.evaluate-measure/compile-duration-seconds {}
   :blaze.fhir.operation.evaluate-measure/evaluate-duration-seconds {}
+  :blaze.fhir.operation.evaluate-measure/bloom-filter-creation-duration-seconds {}
+  :blaze.fhir.operation.evaluate-measure/bloom-filter-useful-total {}
+  :blaze.fhir.operation.evaluate-measure/bloom-filter-not-useful-total {}
+  :blaze.fhir.operation.evaluate-measure/bloom-filter-false-positive-total {}
+  :blaze.fhir.operation.evaluate-measure/bloom-filter-bytes {}
 
   ;;
   ;; FHIR Operation GraphQL
@@ -211,6 +216,7 @@
    :kv-store #blaze/ref :blaze.db/index-kv-store
    :resource-indexer #blaze/ref :blaze.db.node/resource-indexer
    :search-param-registry #blaze/ref :blaze.db/search-param-registry
+   :scheduler #blaze/ref :blaze/scheduler
    :enforce-referential-integrity #blaze/cfg ["ENFORCE_REFERENTIAL_INTEGRITY" boolean? true]}
 
   :blaze.db.node/indexer-executor {}
@@ -232,7 +238,7 @@
 
   :blaze.db.node.tx-indexer/duration-seconds {}
 
-  :blaze.db/cache-collector
+  :blaze/cache-collector
   {:caches
    {"tx-cache" #blaze/ref :blaze.db/tx-cache
     "resource-cache" #blaze/ref :blaze.db/resource-cache}}
@@ -274,7 +280,9 @@
   ;;
   :blaze.db/search-param-registry
   {:structure-definition-repo #blaze/ref :blaze.fhir/structure-definition-repo
-   :extra-bundle-file #blaze/cfg ["DB_SEARCH_PARAM_BUNDLE" string?]}}
+   :extra-bundle-file #blaze/cfg ["DB_SEARCH_PARAM_BUNDLE" string?]}
+
+  :blaze/scheduler {}}
 
  :storage
  {:in-memory
@@ -299,6 +307,7 @@
      :resource-as-of-index nil
      :type-as-of-index nil
      :system-as-of-index nil
+     :patient-as-of-index nil
      :type-stats-index nil
      :system-stats-index nil}}
 
@@ -441,6 +450,12 @@
       :target-file-size-base-in-mb 8
       :block-size #blaze/cfg ["DB_BLOCK_SIZE" int? 16384]}
 
+     :patient-as-of-index
+     {:write-buffer-size-in-mb 8
+      :max-bytes-for-level-base-in-mb 32
+      :target-file-size-base-in-mb 8
+      :block-size #blaze/cfg ["DB_BLOCK_SIZE" int? 16384]}
+
      :type-stats-index
      {:write-buffer-size-in-mb 2
       :max-bytes-for-level-base-in-mb 8
@@ -644,6 +659,12 @@
       :target-file-size-base-in-mb 8
       :block-size #blaze/cfg ["DB_BLOCK_SIZE" int? 16384]}
 
+     :patient-as-of-index
+     {:write-buffer-size-in-mb 8
+      :max-bytes-for-level-base-in-mb 32
+      :target-file-size-base-in-mb 8
+      :block-size #blaze/cfg ["DB_BLOCK_SIZE" int? 16384]}
+
      :type-stats-index
      {:write-buffer-size-in-mb 2
       :max-bytes-for-level-base-in-mb 8
@@ -770,6 +791,17 @@
      :scheduler #blaze/ref :blaze/scheduler
      :provider-url #blaze/cfg ["OPENID_PROVIDER_URL" string?]}
 
-    :blaze/http-client {}
+    :blaze/http-client {}}}
+
+  {:name "CQL Expression Cache"
+   :toggle "CQL_EXPR_CACHE_SIZE"
+   :config
+   {:blaze.fhir.operation.evaluate-measure/handler
+    {:blaze.elm.expression/cache #blaze/ref :blaze.fhir.operation.evaluate-measure/expr-cache}
+
+    :blaze.fhir.operation.evaluate-measure/expr-cache
+    {:max-size #blaze/cfg ["CQL_EXPR_CACHE_SIZE" nat-int?]}
 
-    :blaze/scheduler {}}}]}
+    :blaze/cache-collector
+    {:caches
+     {"cql-expr-cache" #blaze/ref :blaze.fhir.operation.evaluate-measure/expr-cache}}}}]}
diff --git a/src/blaze/system.clj b/src/blaze/system.clj
index 0205c8917..39450a766 100644
--- a/src/blaze/system.clj
+++ b/src/blaze/system.clj
@@ -169,7 +169,7 @@
       (let [enabled? (feature-enabled? env feature)]
         (log/info "Feature" name (if enabled? "enabled" "disabled"))
         (if enabled?
-          (merge-with merge res config)
+          (merge-with (partial merge-with merge) res config)
           res)))
     base-config
     features))